In 2004, voters narrowly approved Proposition 63, the Mental Heath Services Act (MHSA), which imposed an additional 1% tax on personal income above $1 million. The funds generated from this “millionaire’s tax” were intended to expand county mental health programs. Taxpayer and business groups opposed the measure for a couple of obvious reasons. First, California is already a high tax, high spending state that didn’t need any more revenue. Second, as we predicted, Prop 63 would exacerbate California’s income tax volatility. Although the final vote for Proposition 63 was tallied more than four years ago, evidence suggests that California’s most...