On the stability of U.S. politics: post-sample forecasts and refinements of the Congleton–Shughart models of Social Security and Medicare benefit levels

An important issue associated with empirical research is the extent to which statistical results continue to hold in the post-sample period. Although many tests of robustness within the period of a given study are routinely reported, relatively little attention is paid to model performance in the post-sample period. This paper examines the post-sample performance of the Congleton and Shughart (Econ Inq 28(1): 109–132, 1990) estimates of three public choice models of Social Security benefit levels. The Social Security program is the single largest line item in the federal budget; so, examining the post-sample performance of the Congleton–Shughart estimates also sheds light on the long-run stability of political processes in the United States. In general, we find that the three public choice models perform well in the post-sample period, although there are several caveats to that conclusion. The results of our post-sample study also suggest that the political processes of the United States with respect to major fiscal policies are more stable and robust than news reports suggest.