Prop. 30 raised the state’s top income tax rate by 8%, increasing it one percentage point from 12.3% to 13.3%, which is now the highest state income tax rate in the nation. Prop. 30 also hiked the tax rate on income between $300,000 and $500,000 by two percentage points, and raised the rate on income in excess of $500,000 by three percentage points.

In 2016, California voters extended the Prop. 30 income tax increases, which were originally scheduled to expire in 2019, until 2030. There will be an effort to extend those income tax hikes yet again prior to their expiration in 2030; book it now.

Varner’s new research examined taxpayers who were and were not hit by the Prop. 30 rate hikes. He found that in the two years before the Prop. 30 tax hike was imposed (2011 and 2012), net in-migration for both groups “was positive and roughly constant.” Yet following 2012 and the passage of Prop. 30, net in-migration dropped for households that were facing an effective tax increase of 0.5 percent or more. The reduction was greatest for households facing the highest effective tax hike, according to Varner and his coauthors, who include Allen Prohofsky of the California Franchise Tax Board.