On the Importance of Inequality in Politics: Duplicate Bills and Bill Co-sponsorship in the U.S. House of Representatives

In this paper, we attempt to provide an economic explanation for the adoption of bill co-sponsorship by the U.S. House of Representatives in 1967. We demonstrate empirically that key features of legislative production prior to 1967 (when House members’ support for a bill was indicated by introduction of duplicate bills) and post-1967 (when political support for a bill is indicated by co-sponsorship) are strikingly similar. Specifically, the raw number of supporters of a bill, whether indicated by duplicate bills or by co-sponsorship, is not nearly as critical to advancement of that bill through the House of Representatives as is the political power of the individual who introduces it and those who support it. The relative sizes of these effects are highly consistent over time. In effect, this finding means that the underlying factors of importance in the House’s legislative production function did not change significantly when bill co-sponsorship was adopted. This suggests that the change in operating procedure may have been driven by an intra-chamber struggle to control the legislative outcomes. We present empirical evidence that is highly consistent with this hypothesis - - adoption of bill co-sponsorship in 1967 coincides exactly with the post-World War II peak in a concentration ratio of legislation passed in the U.S. House of Representatives. Prior to the 90th Congress, there was a more-or-less steady increase in concentration of legislation passed by the five busiest committees that peaked at over 0.4 in the 90th Congress and then declined precipitously to under 0.15 by the 93rd Congress.