Article contents
- Abstract
- Constituent Trade Interests and Factor Mobility
- Data and Hypotheses
- Methods and Results
- Robustness Checks
- Discussion
- Conclusion
- Appendix 1: Trade Policy Votes
- Appendix 2: Additional Roll Call Votes on International Economic Policy
- Appendix 3: Data Sources and Variable Construction Details
- References
Domestic Influences on International Trade Policy: Factor Mobility in the United States, 1963 to 1992
Published online by Cambridge University Press: 04 January 2006
- Abstract
- Constituent Trade Interests and Factor Mobility
- Data and Hypotheses
- Methods and Results
- Robustness Checks
- Discussion
- Conclusion
- Appendix 1: Trade Policy Votes
- Appendix 2: Additional Roll Call Votes on International Economic Policy
- Appendix 3: Data Sources and Variable Construction Details
- References
Abstract
The constituent influences on congressional voting patterns for trade policy have long been an important field of study. A central theoretical component (explicitly or implicitly) of all these studies is the level of factor mobility that defines which constituent coalitions will form and how they will be affected. Yet the recent literature offers contradictory evidence on the current level of factor mobility. Using an original data set of economic demographics of House districts and the roll call votes of U.S. House members on trade policies from 1963 to 1992, I argue that factor mobility was relatively low in the 1960s and 1970s but was rising. The relative level of factor mobility, then, reached a pivot point in the late 1970s and was subsequently relatively high in the 1980s and 1990s. I check the robustness of these results on the expected strength of the political parties in supplying these policies and the effects of divided government.I would like to thank Oksan Bayulgen, Sam Best, Mark Boyer, Stephen Bronars, Walter Dean Burnham, Virginia Hettinger, Alan Kessler, Peter Kingstone, Tse-Min Lin, Robert Moser, Phil Paolino, Dennis Plane, Howard Reiter, Brian Roberts, Ken Scheve, Lyle Scruggs, Mathieu Turgeon, the editor of IO, and two anonymous reviewers for their helpful comments and suggestions. Any errors that remain are, of course, my own.
- Type
- Research Article
- Information
- Copyright
- © 2006 The IO Foundation and Cambridge University Press
As globalization is increasingly affecting individuals, the domestic influences on international trade become especially important to understand. A central aspect of any constituent-based political-economy model of trade policy, explicitly or implicitly, is a theory of intersectoral factor mobility. The level of factor mobility—or the degree of factor specificity—defines the ease with which the factors of production can move among sectors of the economy. As factor mobility varies, so do the expected constituent coalitions for and against trade liberalization. The level of factor mobility, then, is an essential tool in developing theoretical and empirical models of constituent interests for trade policy. Furthermore, the level of factor mobility also has significant effects on an individual's income, the depth and breadth of the economic impact of globalization on society, the ability of the political parties to represent the vying constituent coalitions, as well as on the volume of international trade itself. Thus whether factor mobility is relatively high or low has far-reaching but vastly different consequences in the economy, in society, and in politics.
The level of factor mobility cannot be measured directly. With a few notable exceptions, it and the appropriate modeling of constituent coalitions for and against trade policy are too often assumed or not considered. Thus it may not be surprising that an examination of the literature on recent U.S. trade policy and constituent coalitions does not produce, in the aggregate, consistent conclusions. Although some studies have shown evidence that factor mobility is consistent with it recently being relatively low,1
See, for instance, Hiscox 2002a and 2002b; Magee, Brock, and Young 1989.
See, for instance, Kaempfer and Marks 1993; Scheve and Slaughter 2001b.
See Hiscox 2001, 2002a, and 2002b.
See Hiscox 2002a, 154, and 2002b, 602–3.
In this study, I try to bridge the theoretical and empirical gaps manifested by the seemingly inconsistent findings among the multiple studies that have addressed constituent interests and trade politics in the United States from 1963 to 1992. To do so, I directly test whether factor mobility is relatively low or high and if it changes.5
Determining the precise level of factor mobility is nearly impossible. The purpose here is to provide an insight into the general trend.
Five sections follow. First I present the two main economic theories of factor mobility and constituent interests for international trade, and I examine the aggregate inconsistencies in the current literature. Next I explain the construction of the data set employed and the study's hypotheses. Third I report and discuss the findings; and fourth check the robustness of the findings. I conclude with the theoretical and practical implications of the study.
Constituent Trade Interests and Factor Mobility
Constituent trade interests are modeled by one of two well-established economic theories: the Ricardo-Viner or the Stolper-Samuelson theory. For the purposes of this study, there are three general but critical differences between these models. First, the Ricardo-Viner model assumes that factor mobility is low; the Stolper-Samuelson model assumes that it is high. Second, the models predict different constituent coalitions in society, based on the way that gains and losses in factor income are distributed. The Ricardo-Viner model predicts sectoral constituent coalitions; the Stolper-Samuelson model predicts factoral constituent coalitions. Because factor mobility cannot be both high and low at the same time, the two models are, by definition, mutually exclusive. Over time, however, factor mobility can gradually change and, hence, can exhibit characteristics of a continuous variable.7
Third, the coalitions predicted by both economic models vary considerably in form. When factor mobility is high, the resulting factoral constituent coalitions are, by definition, relatively homogeneous; when factor mobility is low, the resulting sectoral constituent coalitions are, by definition, relatively heterogeneous.8See Alt and Gilligan 1994, 188; Hiscox 2002a, 5, 36; Hiscox 2002c, 7–8; Olson 1982.
Specifically, the Stolper-Samuelson model assumes that the factors of production—labor and capital—are mobile, and thus the model derives preferences and predicts coalitions based on the relative abundance or scarcity of the factors.9
Consistent with many recent works on the United States, the factor of land is omitted.
See, for instance, Mayer 1984, 973–74; Scheve and Slaughter 2001a, 48–51.
See, for instance, Rogowski 1987 and 1989.
The Ricardo-Viner model assumes that the factors of production are “sticky” and cannot be reallocated swiftly to more efficient sectors of the economy.12
See Alt and Gilligan 1994 for an excellent description of the full logic of the Stolper-Samuelson and the Ricardo-Viner models.
The Ricardo-Viner and the Stolper-Samuelson theories are ideal-type theories. Using these models is empirically useful, as I discuss below, even though the actual level of factor mobility is unlikely to conform to their idealized assumptions. Instead, because the level of factor mobility is likely to gradually change over time, it is a secular trend.13
As the actual level of factor mobility gradually moves along a continuum between the two ideal types, there should be a pivot point that distinguishes the two. On one side of the pivot point, factor mobility is relatively low; on other side, it is relatively high. As the median voter's economic interest is tipped from one side to the other, there should be predictable and observable economic and political implications. The level of factor mobility, however, is not directly measurable. It is usually indirectly inferred from these predictable and observable economic and political manifestations, such as the significance of sectoral or factoral variables that influence reelection-minded legislators on trade policy. The aggregate conclusions from such political economy studies of trade policy, however, offer contradictory arguments or evidence on the recent balance of the relative level of factor mobility in the United States. Some have reported evidence of sectoral influence on congressional lobbying and voting behavior.14See, for instance, Deardorff and Stern 1998; Destler 1986; Destler and Odell 1987; Hiscox 2002a and 2002b; Magee, Brock, and Young 1989; McArthur and Marks 1990; McGillivray 1997; Nollen and Iglarsh 1990.
See, for instance, Kaempfer and Marks 1993; Midford 1993; Rogowski 1987 and 1989.
See, for instance, Baldwin 1985; Baldwin and Magee 2000; Coughlin 1985; Marks 1993; McArthur and Marks 1988; Tosini and Tower 1987.
First, most of the studies are concerned not with determining the relative level of factor mobility but with modeling other phenomena. In such cases, factor mobility is frequently assumed, if it is considered at all, to be either low or high. For this reason, the tested constituent economic variables may represent just one of theories, both theories, or parts of each. Because the two models are theoretically mutually exclusive, however, methodological concerns arise when the two models are tested simultaneously. Nonetheless, because factor mobility can vary continuously between the two ideal-type models, it is possible that both sectoral and factoral variables may be significant. As this study emphasizes, however, the balance between relatively low and high factor mobility has important political and economic implications that are best informed by evaluating the comparative performance of each model.
Second, in that the relative level of factor mobility varies, it is possible that at some point during the thirty years that the balance between the two ideal-type models has changed. For instance, empirical evidence may show that during one Congress sectoral influences are more significant and during a subsequent Congress, factoral influences are more significant. This would be theoretically consistent only if the relative level of factor mobility has also changed accordingly. Similarly, if roll call votes are pooled together over a time period in which the balance between relatively low and relatively high factor mobility changes, the tests may produce seemingly contradictory results.
Third, the scope of studies on the domestic influences on trade policy range from analyses of a single roll call vote in one Congress to analyses of roll call votes over nearly two centuries. Given the limitations of available data, particularly for the latter, some of the studies have used state-level data to predict voting patterns in the House. Though this may provide uniformity over time, it raises concerns of ecological fallacies and spurious results.
The current literature has provided valuable results, but this study differs from and contributes to the literature in at least three ways. First, to accurately model the effects of constituent interests on the voting behavior of members of the House, I use House-district-level economic data and analyze each of the fifteen Congresses individually. I use U.S. Census labor and economic data on each of the twenty two-digit Standard Industrial Classification (SIC) manufacturing sectors, and national data on exports, imports, and capital to create a data set of economic demographic variables for each House district over the thirty years for each of the factoral and sectoral coalitions for and against trade liberalization. Testing data across consistent geographic units has been lacking, largely because of the difficulties in collecting and coding disaggregated Census data. This data set, however, provides unit consistency between detailed district-level constituent economic interests over time and House roll call voting.
In addition, the district-level economic variables that I employ discretely capture each of the four possible constituent coalitions: export-competitive versus import-competing sectors or capital versus labor. These four coalitions can be considered input variables that influence rational legislators and can be used to reveal their preferences.17
The use of revealed preferences is a common technique in analyzing trade policy. See Bailey and Brady 1998; Bailey, Goldstein, and Weingast 1997; Gartzke and Wrighton 1998; Gilligan 1997; Irwin and Kroszner 1999; Hiscox 2002a and 2002b; Magee, Brock, and Young 1989.
See, for instance, Hiscox 2002a and 2002b; Kaempfer and Marks 1993.
See, for instance, Rodrik 1995; Scheve and Slaughter 2001a and 2001b.
The second difference between this study and many of the previous studies is the concentration on determining the balance between relative low and high factor mobility. Significant exceptions to this include.21
See Hiscox 2002a and 2002b; Scheve and Slaughter 2001a and 2001b. Scheve and Slaughter 2001b analyze the 1993 American National Election Survey and find evidence of factoral influences. Though the year 1993 follows the last year of this study, it is included in Hiscox last time period of 1970 to 1994. Similar to some of the cited studies, they come to different conclusions.
The third difference between this study and many of its forerunners is its extension of factor mobility's predictable political consequences: in particular, the ability of political parties to consistently and coherently represent constituent interests, as well as the effects of divided government on trade liberalization. Analyzing two political consequences of changes in the balance of the relative levels of factor mobility provides a stronger theory and a robustness check on the initial empirical findings. Furthermore, the inclusion of political parties and divided government in the analysis aids in accounting for politically endogenous outcomes.
Factor mobility affects political parties by changing the relative level of homogeneity of constituent coalitions.22
See Alt and Gilligan 1994, 188; Hiscox 2002a, 36, and 2002c, 7–8.
Alt and Gilligan 1994, 188.
Alternatively, when factor mobility is low, an industry that is disadvantageously positioned in the international economy may quickly find its competitiveness changed through, for instance, technological advances. Also, the costs and benefits of international competition are largely limited to the exporting and importing industries. As the income effects are distributed across just the tradable sectors and not more broadly between the classes, there are few income externalities in the nontradable industries. Hence, the sectoral constituent coalitions produced are characterized by fragmented and ephemeral alliances: in other words, they are heterogeneous. Consequently, periods of relatively low factor mobility produce relatively weak constituent coalitions on issues of trade liberalization and, consequently, each party will have a relatively weak constituent foundation on which to base policy alternatives.
In sum, the balance of the relative level of factor mobility affects the degree of constituent homogeneity on trade policy issues.24
The overall homogeneity of partisan constituent coalitions and the strength of the political parties have many contributing influences. This study focuses on just one: factor mobility.
This theory is referred to as Conditional Party Government. See, for instance, Aldrich 1995; Aldrich and Rohde 2001; Rohde 1991.
Ibid., 99. Hiscox 2002c, 7–8, makes this pair of arguments as well: low factor mobility facilitates weak parties and high factor mobility facilitates strong parties.
See, for instance, Hibbs 1977; and Sundquist 1983.
I would like to thank the editor for emphasizing this point.
The introduction of party politics, however, raises the important and much debated issue of the effects of partisan control of branches of the federal government; in other words, the effects of divided government on trade liberalization. For instance, O'Halloran and Lohmann and O'Halloran argue that legislators in unified governments are more likely to grant trade-making authority to the president, and that legislators in divided governments are less likely to do so.30
See O'Halloran 1994, 118; Lohmann and O'Halloran 1994. See also Epstein and O'Halloran 1996; Milner 1997; Milner and Rosendorff 1996; O'Halloran 1994; Sherman 2002.
Karol 2000. Specifically, since the passage of Reciprocal Trade Agreement Act in 1934, presidents have tended to support freer trade. See, for instance, Bailey, Goldstein, and Weingast 1997; Destler 1995; Gilligan 1997.
Karol 2000, 841.
See, for instance, Gibson 2000; Keech and Pak 1995.
These studies on divided government, however, understate or do not address the relative level of factor mobility and the changing strength of the political parties. Once the latter are considered, then it is logical to theorize that the effects of unified/divided government matter most when the parties are strong and stand for clear and consistent policy alternatives. Therefore, the effects of unified/divided government ought to be mitigated when factor mobility is low because the relatively heterogeneous constituent interests for trade policy weaken the party-constituency bonds. Conversely, the effects of unified/divided government ought to be more prominent when factor mobility is high because of the relatively homogeneous and polarized party-constituency bonds. Even though the relative free-trading position of the president may also be affected by partisanship,34
a general degree of presidential liberalism is assumed. Thus if the parties are strong and the majority congressional party consists of protectionists, divided government should be negatively correlated with trade liberalization; if the majority congressional party consists of free-traders, then divided government should be positively correlated with trade liberalization.35This general theoretical construction depends on the position of the status quo and does not consider other possibilities. A more extensive discussion, however, is beyond the scope of this article.
Karol 2000, 827–29, fn. 15.
Data and Hypotheses
The rational decisions of reelection-minded legislators are commonly used to reveal the preferences of their constituents. In this case, the influence of constituent coalitions on legislators' trade policy roll call votes can be employed as a measure of the relative strength of sectoral and factor coalitions as a proxy for the relative level factor mobility. Thus I use a dependent variable of roll call votes on trade policy in the House from 1963 to 1992 for all of the initial regressions.38
The time period is chosen for two reasons. First, it begins after the release of the 1960 U.S. census and the subsequent House reapportionment. The 1960 census provides substantially better data than any time period before 1960. The economic data are not available for the entire 1993 to 2002 period, thus they are not included.
To ensure that there was at least one bill for each Congress, a few commodity specific bills had to be included. This is not optimal. However, most of the bills, if not all, were debated in the House in terms of the direction of national trade policy. See the Congressional Quarterly Almanac various years for the determination of “important” legislation and the substance of the debates.
A minimal amount of competition is defined as at least 100 yea and nay votes for each roll call.
See, for instance, Destler 1995; Gilligan 1997; Hiscox 2002a and 2002b; Kaempfer and Marks 1993; Karol 2000; McArthur and Marks 1988; Marks 1993.
Hiscox 2002b, 606.
Only votes of yea or nay are recorded. All other (non)votes are coded as missing.
At first, only one vote is analyzed in each Congress to facilitate the specific requirements of the statistical tests used. See the methods section below.
The two economic models of factor mobility suggest that constituent divisions will either be along sectoral lines if factor mobility is relatively low or along factoral lines if it is relatively high. For each division, there are interests that are advantaged by liberalization and interests that are disadvantaged. Thus there are four possible economic coalitions (in two exclusive groupings) for trade policy interests: export-competitive industries versus import-competing industries (sectoral division) or capital versus labor (factoral division). The former in both cases is expected to support trade liberalization. From this I am able to construct specific assumptions and hypotheses. First I assume that the two coalitions that are advantageously affected by trade liberalization (exports or capital) will positively influence legislators' votes for trade liberalization. Second I assume that the two coalitions disadvantageously affected (imports or labor) will negatively influence legislators' votes for trade liberalization. Third I expect that the sectoral variables will better characterize the 1960s and the 1970s. Fourth I expect that the factoral variables will better characterize the 1980s and 1990s. In other words, I expect that factor mobility was relatively low in the 1960s and 1970s, but was rising and reached a pivot point in the late 1970s. Subsequently, factor mobility has been relatively high in the 1980s and 1990s.
H1: I expect that the sectoral variables will better characterize the 1960s and 1970s
H2: I expect that the factoral variables will better characterize the 1980s and 1990s
The variables for exports, imports, and capital are all constructed using a similar method that creates a unique score for each congressional district for each Congress for each variable. In general, district-level economic demographic data are weighted by a measure of U.S. exports, imports, or capital stock. Bailey, Goldstein, and Weingast and Irwin and Kroszner use a similar variable construction to represent constituent economic interests.45
Specifically, the base district-level economic data record the number of each of the twenty manufacturing industries (based on each of the two-digit SIC codes) in each congressional district for each year from 1963 to 1992.46This is the primary difference from the constructions of Bailey, Goldstein, and Weingast 1997; and Irwin and Kroszner 1999. The former also uses the total number of industries but includes an additional weight of total number of manufacturing employees; see Bailey, Goldstein, and Weingast 1997, 337. The additional weight is not used here because it is the labor variable. The latter uses sectoral-based product output but also tests a measure that approximates Bailey, Goldstein, and Weingast's; see Irwin and Kroszner 1999, 669. The two measures are highly correlated and produce similar results, see Irwin and Kroszner 1999, fn. 29. The present choice of construction was also constrained by the availability of county- and/or district-level data over the thirty-year time span.
The same weight construction is used in Bailey, Goldstein, and Weingast 1997; Irwin and Kroszner 1999.
For the capital variable, the weight is the national level of the current-cost gross stock of fixed private capital for each of the twenty sectors for each year measured in millions of dollars. The annual capital stock for each sector is then multiplied by the base congressional economic data by sector for each year. Same as the construction of the exports and imports variables, the sectors are averaged for each Congress and aggregated across sectors to produce a unique score of capital investment for each congressional district for each Congress. This measure is an improvement over most other measures because it uses the same base congressional economic data as exports and imports, thereby making comparisons more reliable. Moreover, it better captures the level of capital investment in manufacturing sectors at the congressional-district level. For the labor variable, the labor figures for the twenty manufacturing industries for each congressional district are available. I simply sum the twenty figures and hence a composite index is not needed. The annual labor data are then averaged across the two years that correspond to each Congress. For the regressions, the capital and labor variables are multiplied by a scalar of 1/1000000 and 1/10000, respectively, so that the coefficients are easier to display. See Appendix 3 for details and data sources.
Methods and Results
The first step in testing the hypotheses is to determine which economic model best fits the data on constituent interests—in other words, to determine whether factor mobility is relatively low or high and when the balance between the two may change. Because the ideal types of the economic models are mutually exclusive, one of the models cannot be reduced to the other by a set of linear transformations. As such, the two economic models are considered nonnested and should not be regressed together.48
See Davidson and MacKinnon 1981; Greene 1997, 364–69; Johnston and DiNardo 1997. For a specific discussion of nonnested models applied to international relations, see Clarke 2001.

where X1 and X2 are the exports and imports variables, and X3 and X4 are the capital and labor variables.49
For simplicity, the models are presented in a generic functional form and the intercepts are omitted. The same error structure is assumed across models.
Assume, however, that one were to test a third “supermodel,” Ht, which is a combination of the Hss and Hrv. Then, one would write:

Here one is assuming that the models are nested because, for example, if the coefficients of the Hss model, β3 and β4, are restricted to 0, then Ht is the same as Hrv. Model Ht, though, makes the contradictory assumption that factor mobility can be both low and high. This obviously cannot be the case. Thus the two different and opposing theories necessitate two different models: Hrv and Hss. Clarke demonstrates that nonnested models regressed together in one “supermodel,” such as in Ht, has the potential of producing unreliable results.50
The difficulty, then, becomes comparing the two models head-to-head. To do so, I use the same procedure, the J-Test, as did Hiscox.51
This procedure uses an indirect linear combination of the two models to determine which one (if either) better fits the data. Specifically, the predicted values from the first economic model, Hrv, are included in the second economic model, Hss, as a new variable and retested; the process is then repeated with the predicted values from the second model retested in the first. The coefficients that are produced for the predicted value variables are essentially the weight given to that model and can be directly compared. If only one of the two coefficients for the predicted value variables is significant, then that model outperforms the other (because the insignificant coefficient indicates that that model's weight cannot be distinguished from zero). If both coefficients are significant or neither is significant, then the result is indeterminate and the appropriate model cannot be assessed.The J Test, then, compares the ideal-type theories and generally produces a dichotomous result supporting either Hrv or Hss. As a result, if the sectoral model outperforms the factoral model in influencing policy, then it is logical to conclude that factor mobility must be relatively low. Conversely, if the factoral model outperforms the sectoral model, then factor mobility must be relatively high. This solves the problem of comparing nonnested models but raises another issue. The dichotomous result belies the gradual change that factor mobility as a secular trend is expected to display. Instead, it simply determines which side of the balance between relatively low and relatively high factor mobility the data better fit. Thus a shift in the balance may appear to be discontinuous even if it is not. Although less than optimal, this is a methodologically necessary concession. I attempt to accommodate this, however, through a graphical examination of the probability of each model's statistical significance.
Because the roll call vote takes only the value of 0 (antiliberalization) or 1 (proliberalization), probit is used to estimate each model. For each Congress only the economic variables from the models are regressed on the roll call vote. As discussed above, other factors such as the legislator's party affiliation and divided government may also influence voting behavior on trade policy. These additional variables will be included in the robustness checks, but they are omitted from the J Tests to maintain consistency with other studies of factor mobility. Specifically, Hiscox estimates the effects only of constituent economic variables and argues that he “exclude[s] [controls for party affiliation] to provide the clearest imaginable test between the class and the industry-group models.”52
Hiscox 2002b, 599.
J Tests of models of factor mobility, 1963–92

The results shown provide a measure of the general trend of factor mobility through the applicability of each model. In ten of the fifteen Congresses, the null hypothesis of only one of the two economic models is rejected. This allows one to say which model is statistically more appropriate. In the remaining five Congresses, one cannot decipher the applicability of the two models because either both models are significant or neither model is significant. Specifically, from 1963 to 1978, the Ricardo-Viner model is the only model that is accepted and therefore indicates that the data are consistent with relatively low levels of factor mobility. The Ricardo-Viner model, however, is significant in only half of these Congresses (that is, four of the eight Congresses), which may indicate some weakness in the sectoral variables. Conversely, from 1979 to 1992, the Stolper-Samuelson model is the only model that is accepted. This is the case for six of the seven Congresses. Therefore one is provided with strong evidence consistent with relatively high factor mobility. This is further supported by examining the ratio between the pseudo R squares of the Ricardo-Viner model over those of the Stolper-Samuelson model. From 1963 to 1978, the ratio in all but one case is above 1.0, which indicates that the Ricardo-Viner model is able to explain more variance in the data than the Stolper-Samuelson model. The opposite is true from 1979 to 1992. Both of these measures are consistent with the balance between relatively low and relatively high factor mobility reaching a pivot point in the late 1970s, with relatively low factor mobility beforehand and relatively high factor mobility after.
Factor mobility can change over time, but it is highly unlikely that it will radically swing from one Congress to another. Accordingly, two caveats are in order. First, the statistically ambiguous tests may be because of exogenous forces or idiosyncrasies in the individual pieces of legislation that are examined. Particularly given the heterogeneous nature of sectoral coalitions, it is not surprising that aggregate measures of exports and imports are significant less often than aggregate measures of capital and labor. (This is also evident in Table 2.) Second, this may also be because of the sectoral coalitions of relatively low factor mobility gradually weakening and approaching the pivot point between it and relatively high factor mobility. This gradual process becomes more apparent if one graphically examines the data over time; Figure 1 does so by plotting the moving average of the p-values of the z-scores from each model over time. The p-values are the probability that each model is significant; the area below the provided 0.05 line indicates statistical significance.53
Because the moving average is used—in order to mitigate outlying results—the horizontal line at 0.05 does not actually represent statistical significance. It is used only illustratively.
Appropriate economic model tested on trade liberalization


Changing levels of factor mobility
Using the pivot point that defines the period of relatively low from relatively high factor mobility, I report in Table 2 the probit results from each of the appropriate economic models that were used to generate the J Test results and Figure 1. Because the evidence was consistent with factor mobility being relatively low from 1963 to 1978, the Ricardo-Viner model (that is, export-competitive versus import-competing industries) is reported for these years plus the 96th Congress.54
The 96th Congress is reported with both the sectoral and the factoral variables because the data indicate that it is the tipping point between relatively low and relatively high factor mobility.
Imports are significant but positive for the 94th Congress. This is most likely an artifact of the specific legislation analyzed. Particularly, one of the amendments to the Bretton Woods agreement allowed for flexible instead of fixed exchange rates. Given the economic context and the artificially strong dollar in the early 1970s, importers may have believed that floating exchange rates would weaken the dollar and, thus, make imports more expensive, which would, of course, be advantageous to sectors of the economy that experience high import competition. Regardless of the direction of this sectoral variable, the Ricardo-Viner model nonetheless outperforms the Stolper-Samuelson in the 94th Congress.
After 1979 the results from the J Tests are indicative of a relatively high level of factor mobility. Thus the variables from the Stolper-Samuelson model (that is, capital versus labor) are reported. In these regressions, eleven of the fourteen coefficients are statistically significant and all are in the expected directions. Districts with relatively capital-intensive interests favored trade liberalization; those with relatively labor-intensive interests did not. This is consistent with the assumptions and Hypothesis 2. Because the relative level of factor mobility can be derived from the significance of the two models and their specific economic coalitions, these data are also indicative of a gradual trend from relatively low factor mobility to relatively high. Again, there is naturally a pivot point between the appropriateness of the two ideal-type models in which the influence of the sectoral variables of relatively low factor mobility should gradually cease to explain as much variance as the factor variables of relatively high factor mobility. Tables 1 and 2 do not allow one to demonstrate this gradual secular trend well. Instead, they simply allow one to determine which side of the balance the data best represent. Despite this methodological concession, the evidence is consistently indicative of a change in the level of factor mobility from relatively low to relatively high during the late 1970s.
Robustness Checks
One way to test the robustness of these results is to determine if other expected effects of low and high factor mobility are also present. As discussed above, the coalitions predicted by the relative level of factor mobility vary in their relative homogeneity. The sectoral coalitions of relatively low factor mobility are relatively heterogeneous; the factor coalitions of relatively high factor mobility are relatively homogeneous. If the sectoral variables consist of weaker and more ephemeral coalitional partners, then their strength in explaining roll call votes on issues of trade liberalization should also be weaker. I have already provided some evidence that is descriptively consistent with this assumption. The Ricardo-Viner model and its corresponding sectoral variables in Tables 1 and 2 were significant less frequently than the Stolper-Samuelson model and its corresponding factoral variables. This evidence is far from conclusive and could be caused by other affects, but nonetheless, it begins to provide some validity to the results.
To further test the robustness of the results, I expand the analysis to include political independent variables. According to the conditional party government literature, relatively homogeneous constituent interests provide the basis for strong parties overall.56
See, for instance, Aldrich 1995; Aldrich and Rohde 2001; Rohde 1991.
Brady, Goldstein, and Kessler show that during the late nineteenth and early twentieth centuries—a period that Hiscox argues is also characterized by relatively high levels of factor mobility—political parties had a significant effect on trade policy roll call voting. This effect is independent of constituent economic interests.58
Consistent with these findings, I expect that during the 1960s and 1970s when the above evidence indicates relatively low levels of factor mobility, the variable republican should not have a significant impact on trade liberalization votes. This would indicate that the parties do not statistically differ in their voting patterns, and thus do not offer clear and consistent policy alternatives. Conversely, during the 1980s and 1990s, when the above evidence is consistent with relatively high levels of factor mobility, the variable republican should have a significant impact that is independent of constituent economic interests. This would indicate that the parties do offer clear and consistent policy alternatives on trade liberalization issues. Furthermore, Keech and Pak show that the partisan positions on trade liberalization changed during this time period.59 Specifically, during the 1970s, the Democrats switched from being the party of free trade to the party of protectionism. Consistent with this, I expect that the republican variable will be positively correlated with trade liberalization during the period of high factor mobility.The other influence on the legislator's vote choice discussed above is the partisan composition of the branches of the federal government. The effects of divided government on trade policy have been extensively debated; these studies, however, have largely overlooked the effects of factor mobility on the constituent interests and the political parties. Extending the logic of factor mobility to the effects of divided government is rather straightforward. If the parties do not offer clear and consistent policy alternatives, then the partisan composition of each branch should be less important. If the parties do offer clear and consistent policy alternatives and, as Brady, Goldstein, and Kessler argue, party strength exhibits a significant and independent effect on legislators' voting behavior, then, divided government should also have a significant and independent effect.60
To evaluate these effects, I create a divided government variable that is coded 0 when the House and the president are from the same party and 1 when they are from opposing parties. Given that the Democrats were the majority party during the entire time period analyzed in this study and that they became the party of protectionism during the 1970s concomitantly with the parties gaining strength, I expect that the divided government coefficient will be insignificant when factor mobility is low, and significant but negative during the period of high factor mobility.61A study with a theoretical focus on the effects of divided government would benefit from a greater range of cases than can be offered here.
H3: republican is expected to be insignificant during periods of relatively low factor mobility.
H4: republican is expected to be significant and positively correlated with trade liberalization during periods of relatively high factor mobility.
H5: divided government is expected to be insignificant during period of relatively low factor mobility.
H6: divided government is expected to be significant and negatively correlated with trade liberalization during periods of relatively high factor mobility.
Because divided government does not vary within a given Congress, the data must be pooled to assess its impact. In order to use the appropriate constituent economic variables, the data are also divided into periods of relatively low and relatively high factor mobility. Similar to the J Tests, this construction is not ideal because it may obfuscate the gradual nature of any change. I try to accommodate this again by graphically documenting the trends in partisan support for trade liberalization by Congress.
The dependent is again dichotomous, thus as before, probit is used. However, members in one Congress may be the same members in another Congress, and thus the independence assumption is violated. To account for this, I use Huber and White corrections to produce robust standard errors. The first two columns of Table 3 show the results from the regressions of the economic and political variables on the pooled trade votes used above. In the first column, the two economic variables for the Ricardo-Viner model are significant and in the expected direction. However, the coefficient for republican is not significant—also as expected. In other words, the political parties did not provide statistically clear and consistent alternatives on trade policy during the 1960s and 1970s. Given the lack of clear partisan policy positions on trade liberalization, there is little reason to assume that the partisan composition of the branches of government should be significant. As expected, then, divided government is also not significant during the pooled years 1963–78, that are characterized by relatively low levels of factor mobility. Thus when constituent economic interests based on relatively low factor mobility are controlled, the political variables do not have an independent effect. This is consistent with the hypothesis that sectoral coalitions produce weak and ephemeral political alliances and thus do not provide a strong foundation for the parties consistently to offer clear policy alternatives on trade liberalization.
Robustness test of factor mobility

In the second column of Table 3, the factoral variables of relatively high factor mobility are used. Both capital and labor are again significant and in the expected directions. In this case, though, both republican and divided government are also significant, each in its expected direction. The positive correlation between republican and trade liberalization indicates that Republicans more clearly and consistently supported liberalization than did the Democrats. I expected that if this is the case, then divided government should also have a significant effect, as it does. The significant and negative coefficient of divided government indicates that the majority-Democratic House is less likely to support trade liberalization when the president is a Republican. These robustness checks are supportive of the primary findings of a gradual change from relatively low factor mobility to relatively high factor mobility during the 1970s. Moreover, because constituent economic interests are controlled, the results also lend additional evidence to the Brady, Goldstein, and Kessler argument that the manifestations of party strength extend beyond direct constituent representation.62
I add the caveat, though, that the presence of relatively homogeneous constituent interests seems to be a necessary condition, and, in the case of trade policy, that is consistent with periods of relatively high levels of factor mobility.To further check the robustness of the results, I expand the number and content of the roll call votes used in the dependent variable to ascertain whether the results were merely an artifact of the trade policy votes initially chosen. The number of votes is increased from fifteen to forty-five, a quantity significantly greater than are analyzed in most other trade policy studies. The expanded dependent variable consists of additional trade issues as well as such other international economic policy issues as monetary policy. Changes in monetary policy have a direct effect on the exchange rate, which, in turn, can cause constituent-level economic effects similar to those caused by changes in tariff policy. Bearce and Freiden argue that trade economic models can therefore be used to examine the constituent effects of monetary policy.63
See Bearce 2003; Freiden 1996 and 2002.
I selected additional roll call votes and coded them using the same guidelines as used in the initial selection of trade policy votes. For each Congress, I included two additional votes that had at least a minimal amount of competition and offered the clearest purchase on the policy issue. I coded each as either proliberalization or antiliberalization. I coded each legislator, then, 1 if he or she voted in favor of liberalization and coded a 0 if he or she voted against.64
Consistent with Bearce 2003, the monetary policy votes were coded as proliberalization if the legislation encourages monetary convergence and antiliberalization if the legislation encourages monetary autonomy.
This variable could not be easily used in the initial J Tests because the predicted values are based on multiple cut points.
Only legislators that voted on all three bills for each Congress are included.
As before, the two models based on the relative level of factor mobility are used; columns (3) and (4) of Table 3 report the results. As expected, the sectoral variables in column (3) do not perform well with the broader dependent variable. Still, when exports is significant, it is positive; imports is not significant. The latter is descriptively consistent with the assumption that weaker coalitions of relatively low factor mobility can experience cross-cutting pressures and hence may be less potent in influencing a broader set of policy issues. Unlike the test on trade votes in column (1), republican is significant in column (3). The negative coefficient, though, is consistent with Keech and Pak's argument that the Democrats were more supportive of liberalization during the 1960s and early 1970s than the Republicans.67
Keech and Pak's 1995.
Column (4) reports the results from the period with relatively high factor mobility. All of the variables are significant and in the expected direction. capital is positively and labor is negatively correlated with trade liberalization. As expected, the republican coefficient is also significant but changes direction from the 1963 to 1978 analysis in column (3). In this case, the partisan effect is also much greater. For instance, holding all of the other independent variables at their means but allowing republican to vary from 0 to 1 increases the probability that a legislator will vote in favor of liberalization on all three pieces of legislation by 37.48 percent.68
The cut point at 3 is used again for comparative purposes even though it does not produce the largest probability this time. Instead, the cut point at 0 produces a probability that a Democrat with identical constituent economic interests as a Republican is 50.36 percent more likely to vote against trade liberalization in all three pieces of legislation.
Viewing the data graphically for each Congress shows a more gradual pattern of increased partisanship over issues of liberalization than is evident in the split pooled cross-sectional analyses of Table 3. In Figure 2, I plot the moving average of three variables that represent party strength in the House from 1963 to 1992. The dark line is the Average Party Unity (APU) scores, the aggregated difference between the percentages of each party voting yea on each piece of legislation for each Congress. As Rohde argues, this is the best measure to determine how internally united and externally divided the parties are—in other words, how strong they are. The trend displays a significant increase in party resurgence beginning in the late 1970s and early 1980s.69
This trend has led many scholars to declare that the political parties are once again strong.70See, for instance, Aldrich 1995; Bond and Fleisher 2000; Hetherington 2001; Rohde 1991.

Average party unity, 1963–92
The two light lines in Figure 2 (one with square and one with triangular data point markers) are the APU scores for the trade votes and for the international economic policy votes, respectively. Both exhibit a similar pattern over these issues: trending from partisan dealignment to partisan realignment. During the latter, the parties offer clearer and more consistent partisan policy alternatives. The international economic policy APU scores, however, begin to show the partisan realignment sooner than the trade policy APU scores. In both cases, the 1970s is obviously a time of great partisan change. In addition, the trends correspond to the pattern discussed in the decline and resurgence of U.S. political parties' literature, the partisan trade policy literature,71
See, for instance, Destler and Balint 1999; Gibson 2000; Goldstein 1993.
Discussion
The above results both confirm and challenge the existing literature on factor mobility and constituent trade preferences. The results confirm the significance and direction of sectoral constituent interests in the 1960s and 1970s and of factoral constituent interests in the 1980s and 1990s on trade policy. They also clarify some of the aggregate inconsistencies in the literature. For example, Magee, Brock, and Young, Kaempfer and Marks, and Scheve and Slaughter study U.S. trade preferences in one particular time period since 1960.72
Magee, Brock, and Young find evidence that is consistent with low factor mobility in the early 1970s; the others' evidence is consistent with high factor mobility in the 1990s. Under an assumption of constant factor mobility from 1963 to 1992, these conclusions are contradictory. By challenging an assumption of constant factor mobility, however, the findings presented in this article help to rectify these differences. Because the general trend from relatively low to relatively high factor mobility reached a pivot point during the late 1970s, studies of trade preferences of the 1960s and 1970s should find sectoral influences more significant and studies of the 1980s and 1990s should find factoral influences more significant.Other studies have provided longitudinal analyses of trade preferences. Rogowski, for instance, does not test for variability in factor mobility—and, accordingly, the appropriateness of each economic model.73
He assumes that factor mobility is high but finds some contradictory evidence in the United States from 1948 to the early 1980s.74Rogowski 1989, 119–21.
Midford 1993, 538–39.
Ibid., 562–63.
See Hiscox 2002a, 154; Hiscox 2002b, 602–3.
In addition, I have emphasized two methodological points. First, the inclusion of both sectoral and factoral variables in the same model may lead to erroneous results. To test two competing and nonnested models accurately, alternative statistical procedures are required to discriminate between them. Second, case-unit consistency between the geographic dimensions of the economic and political variables, in this case House districts, produces results that are more reliable. No doubt, this type of detailed economic data is not consistently available for studies such as Hiscox's that cover two centuries. Nonetheless, empirical constructions that are not unit consistent may also obscure trends that are indeed present.
This study, then, provides the case for a gradual increase in factor mobility with the balance between relatively low factor mobility and relatively high factor mobility reaching a pivot point from the former to the latter in the late 1970s. This claim begs the question: What causes factor mobility to change? There are multiple determinants of the level of factor mobility.79
The determinants discussed represent general national level trends. There could, of course, be local contradictions such as housing shortages, additional transportation costs, and the like. The probable presence of such local anomalies ought to have only diminished the reported results.
Kim 1998, 679.
Ibid., 680.
The general economic context also affects the relative level of factor mobility through the decision calculus of individuals.82
Laborers, for example, decide to invest in the optimal type of skill training, either specific or general, depending on the economic environment. In an uncertain world, workers vary their training investment based on expected risk. In an economic environment with low risk (for instance, high employment stability and retention), a worker has an incentive to choose to increase personal returns by specializing. In an economic environment of high risk, however, the same worker foregoes the increased returns of specialization in favor of the greater employment security offered by general skill training. The former decreases factor mobility; the latter increases it. Grossman and Shapiro conclude optimistically: “factor mobility is more likely to be observed when it is most important that factors be mobile.”83Grossman and Shapiro 1982, 1068.
Their conclusion implies that during periods of economic stagnation and increased job churning, one should witness individuals making investment decisions that increase their ability to be mobile. In this vein, Boisjoly, Duncan, and Smeeding demonstrate that from 1968 to 1992, all labor groups except government workers experienced increasing incidence of involuntary job loss.84
Despite the perception of relatively tight labor markets in the 1990s, Farber shows that involuntary job loss rates were even higher in the 1990s than in the 1980s.85 Furthermore, displaced workers that were reemployed suffered “significant earnings declines relative to what they earned before they were displaced.”86Ibid., 1.
Ibid., 9.
Schmidt 1999, S128.
Dynamic factor mobility is not limited to labor. Grossman also constructs a theoretical model of changing degrees of capital mobility.90
Grossman 1983. See also Brawley 1997 for a direct application of this model to the case of imperial Germany.
Although the theories are clear on this point, the empirical conclusions have been mixed on the extent of trade's influence on growing income disparity. See Slaughter 2000 for a survey of the literature.
One economic trend that seems to be at odds with a gradual increase in the level of factor mobility is the tremendous concomitant growth in intraindustry trade. If factor mobility is relatively high, countries that are endowed with abundant capital, for instance, should gain from trade with countries endowed with abundant labor. Intraindustry trade, though, is typically among capital-abundant northern countries. This conventional wisdom, however, has been theoretically and empirical challenged. When technological differences among northern countries are considered, “it is possible to have a strictly conventional [factoral] model in which the volume of North-North trade exceeds that of North–South trade.”94
Davis 1997, 1060.
Finally, it is important to note that in analyzing aggregate district interests and the revealed preferences of legislators through policy votes, it is difficult to isolate the economic links.95
For an excellent discussion of this, see Magee, Brock, and Young 1989.
Others that discuss or test these relationships include Alt and Gilligan 1994; Bailey 2001; Epstein and O'Halloran 1996; Mayer 1984; McGillivray 1997; Rodrik 1995; Scheve and Slaughter 2001a; Verdier 1994.
Destler 2001, xi.
Conclusion
As economic globalization intensifies, the domestic influences on international trade policy become ever more important to understand. A central variable in the formation of domestic trade preferences and constituent coalitions is the mobility of factors. The analysis presented in this article is consistent with factor mobility being relatively low but rising during the 1960s and the 1970s, reaching a pivot point in the late 1970s and subsequently remaining relatively high during the 1980s and the 1990s. Furthermore, the constituent coalitions are shown to influence the voting behavior of legislators in a manner consistent with economic theory. Constituent coalitions of exporters and capital are positively correlated with trade liberalization, and coalitions of importers and labor are negatively correlated with trade liberalization. I have also shown that the level of factor mobility and the coalitions' predicted level of homogeneity are significantly correlated with the strength of the political parties in supplying trade policies and the influence of divided government.
The relationship among constituent interests, trade policy, and political institutions is dynamic and continues to deserve much greater attention. Further study in this area is crucial not only for an improved understanding of the political system but also as a means of better isolating economic phenomena. Toward this end, this study sheds theoretical light on some of the empirical discrepancies currently present in the literature on trade preferences and policy by using a more detailed data set of constituent economic interests and challenging the theoretical assumption of a constant level of factor mobility. Finally, the relative level of factor mobility is likely to have profound effects on the distribution of income as well as on numerous other policy areas: for instance, immigration policy. As such, using factor mobility to explore political and economic phenomena should continue to be a fertile area of research.
Appendix 1: Trade Policy Votes

Appendix 2: Additional Roll Call Votes on International Economic Policy

Appendix 3: Data Sources and Variable Construction Details
The base economic data are constructed from three sources. Together, these sources provide data on the number of the twenty manufacturing industries based on the two-digit SIC classifications (see below) in each U.S. House district for each year from 1963 to 1992. First, for the years 1963 to 1972 (the first two years of the subsequent decade are included because redistricting after that decade's census had not yet occurred), the data are found in the Congressional District Data Book (Districts of the 88th Congress). Here, the data are presented for the twenty manufacturing sectors already aggregated into House districts. Unlike the data for 1973 and after, the Congressional District Data Book provides data only on firms with twenty or more employees. Second, for the years 1973 to 1976, the data are aggregated only at the subcongressional level (that is, county and independent city). The data for the 3,143 subcongressional units can be found in the Census of Manufacturers, 1972. Beginning in 1977, a digital copy of annual data from County Business Patterns, various years, is available at the I.C.P.S.R. Accordingly, from 1977 to 1992, I use the annual data at the subcongressional unit level for each of the twenty manufacturing sectors. Because the annual data are not available before 1977, the base economic data from 1963 to 1972 and from 1973 to 1976 are held constant.
The subcongressional data (1973 to 1992) are then aggregated into their appropriate congressional district. If one of the subcongressional units was entirely contained in one congressional district, it was simply coded for that House district. If one of the subcongressional units is not entirely so contained but divided between two or more congressional districts, the base economic data for the subcongressional unit is weighted by the percentage of the population of the unit that lives in each corresponding congressional district. From 1972 to 1982, the population percentages are calculated using the 1970 Census of the Population, Characteristics of the Population for each state. From 1983 to 1992, the 1980 Census of Population and Housing: Congressional Districts of the 98th Congress for each state is used. In both cases, the base economic data are then aggregated into the appropriate House districts. Together with the House data from the Congressional District Data Book, the base of congressional economic data is created that provides a detailed demographic account of the number and type of manufacturing industries found in each congressional district for each year from 1963 to 1992.
Next, the base congressional economic data is weighted by annual national level economic data for exports, imports, and capital stock, respectively. The data for the value of the exports and imports can be found in U.S. Census Bureau, U.S. International Trade in Goods and Services, series FT-900, various years. The domestic value of production (GDP) by industry is found in the U.S. Bureau of Economic Analysis, Survey of Current Business, various years. The gross stock of fixed private capital is found in the U.S. Bureau of Economic Analysis, Survey of Current Business, various years. For the years 1963 to 1972, the number of laborers in each congressional district as found in the Congressional District Data Book is weighted by the annual percentage of the national rise or decline in manufacturing jobs. For the years 1973 to 1976, the number of laborers in each of the subcongressional units (as found in the Census of Manufacturers, 1972) is aggregated into congressional districts using the same process as described above and is weighted by the annual percentage of rise or decline in manufacturing jobs in each state.
The following are the manufacturing sectors and their SIC number:
20. Food and kindred products
21. Tobacco manufactures
22. Textile mills products
23. Apparel and other textile products
24. Lumber and wood products
25. Furniture and fixtures
26. Paper and allied products
27. Printing and publishing
28. Chemicals and allied products
29. Petroleum and coal products
30. Rubber and plastic products
31. Leather and leather products
32. Stone, clay and glass products
33. Primary metal industries
34. Fabricated metal product
35. Machinery, except electrical
36. Electrical equipment and supplies
37. Transportation equipment
38. Instruments and related products
39. Miscellaneous manufacturing
References
REFERENCES

J Tests of models of factor mobility, 1963–92

Appropriate economic model tested on trade liberalization

Changing levels of factor mobility

Robustness test of factor mobility

Average party unity, 1963–92
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