Scholars posit that groups play an important role in the legislative process and legislator decision making, but find these questions difficult to empirically study due to the private information exchanges. This article exploits a legislative reporting institution to explore group involvement in policy making. In the California state legislature, extra-legislative individuals or organizations that write legislation and secure a legislator to author the bill may be listed as sponsors. Data come from California bill analyses and extend from 1993 to 2014. This group tactic is frequently used: 40% of bills introduced and over 60% of bills that become law list an extra-legislative sponsor. Group sponsorship is significantly related to passage, even after matching on a number of covariates. Legislators use fewer group bills and substitute out of group bills as they gain experience. Group input serves as an integral part of a legislative portfolio and the agenda-setting stage of legislative decision making.
