This document is about a study by the Urban Institute that analyzes how the legalization of same-sex marriage affects the retirement incomes of older gay and lesbian Americans and the impact on federal government spending and revenues over the next 70 years. The study uses the Urban Institute's DYNASIM microsimulation model to estimate Social Security and pension benefits newly available to legally married same-sex couples, project changes in participation in government programs like Social Security and Medicare, and calculate changes in federal tax revenues. The report finds that legalizing same-sex marriage increases retirement incomes for gays and lesbians in the bottom three-fifths of the income distribution, reduces poverty rates, and has a small net negative impact on the federal budget, increasing the deficit by a few billion dollars per year.