The study published in American Political Science Review also said low salaries for state legislators act as a check on bills benefiting small groups of people.
Thad Kousser, a fellow of the Hoover Institution at Stanford University, and Gerald Gamm, an associate professor of political science and history at the University of Rochester, examined state legislatures for the past 120 years. They found the bigger the edge a majority party had, the more special-interest legislation passed.
"For healthy policy, an ounce of competition is worth a pound of cure," Gamm said. "Stiff competition gives political parties a greater incentive to build their collective reputation with statewide legislation and less incentive to focus on localized, non-programmatic politics."
Gamm and Kouser said increasing legislative pay has often been touted as a reform. But they found highly paid legislators have a greater incentive to keep their jobs, which leads to more bills aimed at helping their districts at the expense of the rest of the state.