Gay marriage and the deficit

What would happened if all of America's roughly 600,000 cohabitating gay couples decided to marry?

For one thing, they would all start paying the marriage penalty. Each year, over the next five years, the deficit would fall about $350-450 million per year. Yes that is about one-tenth of one percent of the yearly deficit, but at least a move in the right direction. It is also estimated that social security and related expenditures would increase only slightly as a result of the marriages.

That is from The Atlantic Monthly, October issue, p.64. If you are looking for a good historical introduction to some of the issues surrounding gay marriage, I recommend George Chauncey's recent Why Marriage?.