The Dynamics of Interest Group Evaluations of Congress

The authors apply a dynamic spatial model to interest group ratings of the members of Congress over the period 1959-81. Spatial distances between an interest group and the members of Congress are assumed to be monotonic with the ratings. Their pooled cross-sectional time-series data set consists of 203,387 ratings by fifty-nine interest groups. The authors restrict the spatial coordinates of the interest groups and members of Congress to be polynomial functions of time. Two significant dimensions are recovered: the first dimension, which accounts for approximately 75 percent of the variance, represents liberal-conservative positions on economic issues; the second dimension, which accounts for approximately an additional 5 percent of the variance, represents liberal-conservative positions on social issues. Nearly all the interest groups and most members of Congress are ideologically consistent. They are either liberal on both dimensions or conservative on both. Copyright 1998 by Kluwer Academic Publishers