For many years, personal income tax (PIT) volatility has complicated budgetary planning. This report analyzes the causes of PIT volatility. We find that about 40 percent of PIT volatility is due to choices about which types of income to tax, another 40 percent is due to the progressive rate structure, and the last 20 percent is due to deductions and credits. The Legislature could choose to make the tax less volatile, but actions to reduce volatility could reduce future growth of state tax revenues.