A new study commissioned by open primary advocates claims that nonpartisan primary systems in five states have improved quality-of-life metrics including prosperity, life expectancy and murder rates, though independent political scientists called the findings suggestive but not definitive.

Meanwhile, both parties are increasingly moving to close their primaries, with Republicans and Democrats in multiple states pushing to repeal open or ranked-choice systems, motivated largely by a desire to maintain partisan control over candidate selection.

Richard Barton, assistant teaching professor of public administration and international affairs and author of the study, analyzed 14 metrics and found that states with nonpartisan primaries had seen “statistically significant improvements” in nine of them—even when accounting for other factors.

His research offers case studies to back up his statistical observations. In Louisiana, he argues, nonpartisan primaries had prompted the election of moderate Republican lawmakers who were forced to appeal to a broader coalition of voters. The result: Legislators expanded Medicaid under the Affordable Care Act a decade ago, making Louisiana one of only a few Southern states to do so.

Barton writes that open primaries are “undercutting the power of each party’s ideological base, incentivizing candidates to build broader coalitions.”