I examine the differential responsiveness of U.S. senators to the preferences of rich and poor constituents. My analysis includes broad summary measures of senators’ roll call voting behavior (Poole and Rosenthal’s NOMINATE scores) as well as specific votes on the minimum wage, civil rights, government spending, and abortion. In every instance, senators appear to be much more responsive to the opinions of affluent constituents than to the opinions of constituents with modest incomes. For example, my estimates suggest that constituents at the 75th percentile of the income distribution have almost three times as much influence on senators’ general voting patterns as those at the 25th percentile, and several times as much influence on specific salient roll call votes.
My focus is on votes cast in the U.S. Senate from 1989 through 1994. My measures of constituency preferences are based on survey data from the National Election Study’s 1988-90-92 Senate Election Study. For each of the 50 states I compute the sample average ideology of all constituents (on a general liberal-conservative scale) as well as the average ideology of constituents with each constituent weighted by her family income. Including both of these measures as explanatory variables in statistical analyses of senators’ voting behavior produces small (indeed, often negative) estimated effects of unweighted constituency opinion and large positive effects of income-weighted constituency opinion. These estimates imply that constituents with little or no income receive little or no effective weight in their senators’ voting decisions, while wealthier constituents get responsiveness in rough proportion to their income.
In all of these analyses the voting patterns of Democratic senators are much more liberal than those of Republican senators, even when they represent exactly the same constituents. When Democratic and Republican senators are allowed to attach distinct weights to overall constituency opinion and income-weighted constituency opinion, Republican senators consistently appear to attach relatively more weight to income-weighted opinion than Democratic senators do. However, even Democratic senators appear to attach much more weight to the views of their wealthier constituents than to the views of constituents with modest incomes.
These patterns of disparate responsiveness appear to hold not only for economic issues but also for social issues with little or no discernible economic significance. For example, senators’ votes on a series of bills regarding government regulation of abortion were strongly related to the income-weighted preferences of their constituents on the issue of abortion, but unweighted abortion preferences have no additional effect.
Additional weighting of constituents’ policy preferences by reported turnout, contacting of senators and their staffs, political knowledge, and partisanship sheds some – albeit limited – light on the bases of differential responsiveness. In the domain of ideology the disproportional influence of affluent constituents seems partly attributable to their greater propensity to vote and to contact senators and their staffs. However, in the domain of abortion the impact of income does not seem to be mediated by turnout, contacting, or political knowledge, and may reflect the dependence of elected officials on campaign contributions from pro-choice and pro-life activists.