Cosponsorship in the U.S. Congress
Legislative Studies Quarterly XXII:25-43

Over half of all bills introduced in the U.S. Congress are cosponsored, and, while many observers assume that cosponsorship is crucial to the legislative process, few have analyzed what it means. We view cosponsorship as a signal about the content of legislation and ask whether it is a meaningful signal for members. Specifically we focus on whether cosponsorship influences a bill's passage. Three types of signals are considered: bandwagon, ideological, and expertise. Using data drawn from the 99th Congress, we analyze 8,002 House and Senate bills. Our findings show that cosponsorship is common. However, they also show that it is an overrated cue. At best it provides a signal concerning expertise at the outset of the legislative process, but generates a very weak signal thereafter. In short, cosponsorship has become a routine and rarely effective aspect of the legislative landscape.