When assessing the progressivity of the current retirement system, researchers often focus solely on Social Security while ignoring the value of tax expenditures supporting employer sponsored retirement plans. Social Security replacement rates and the ratio of lifetime payroll taxes to lifetime benefits show that Social Security favors those with low lifetime earnings. However, workers with high lifetime earnings generally benefit more from the federal tax preferences afforded to qualified retirement plans because they contribute more to these plans than low earners and gain more per dollar of contributions from the tax preferences. This study will use the Urban Institute’s DYNASIM microsimulation model to measure the progressivity of the combined tax and benefit system based on the present discounted value of payroll taxes, Social Security benefits, and increased private retirement benefits attributable to the tax preferences for saving in qualified retirement plans. It will examine outcomes under the combined system by income level, Social Security benefit type, marital status, race, education level, and cohort.