While the allocation of interest group monies to specific politicians has been extensively studied, little is known about the factors that determine of the overall level of political activity across groups. We study total contributions by corporate political action committees at the industry level. We create a large data set on industry political activity, covering 124 industries across five election cycles from 1978 to 1986 and sketch out a simple benefit-cost model to predict total corporate PAC contributions in each industry. The few previous studies of this phenomenon use relatively small samples and employ statistical techniques that are either biased or impose untested restrictions. The selectivity-corrected regression technique used here solves these problems. We find that industries with greater potential benefits from government assistance contribute systematically more but that the ability to realize these benefits is constrained by collective action problems facing firms in each industry.

Most work on the allocation patterns of campaign contributions by interest groups focuses on the relative productivity of legislators' effort in serving each group. Short time-series and cross-sectional studies of PAC activity have been done for the House of Representatives and the Senate separately, but no study has used (1) longer time series data or (2) made explicit comparisons among interest group (corporations, unions, and trade associations) activities, considering (3) differences in the time series pattern of groups across the two chambers. We integrate all three perspectives here, using data covering the 1980–1986 election cycles. The results represent preliminary estimates of the dollar value to interest groups of the personal and institutional characteristics of legislators, where these characteristics are allowed for the first time to vary across chambers.