The widespread insolvency of state unemployment insurance (UI) trust funds following the Great Recession has led to renewed interest in reforming states' UI payroll tax systems so as to ensure adequate funding of UI and to distribute program costs more equitably across employers. This paper uses employer-level administrative tax records from Missouri and Washington during 2003-2013 to simulate the effects of several major changes in the UI payroll tax — raising the taxable wage base, raising (and eliminating) the cap on the payroll tax rate, imposing a minimum payroll tax on all employers, and shifting the slope of the tax schedule. The key outcomes we examine are UI payroll tax revenues and measures of cross-subsidization, including a novel measure — the subsidy/tax ratio — that gives an overall picture of the extent of cross-subsidies in a state over a given time period.