Tax reforms in the 1980s changed tax rates and deductions, affecting how much income people reported on their tax returns. The elasticity of reported income depends on available deductions, showing that policymakers can influence this behavior. Broadening tax bases reduces the cost of collecting taxes, with the 1986 Tax Reform Act lowering this cost by 2 cents per dollar of revenue. Half of this reduction came from base broadening and the other half from tax rate cuts. Previous studies' varying estimates on income tax responsiveness can be reconciled through this analysis.