Adriene Hill: Now, to the Republican presidential primary race. Tonight, we have our first debate since Mitt Romney released his tax returns. Romney made $21.7 million in 2010. Much of that from investments he made at private equity firm Bain Capital — even though he retired more than a decade ago.

Marketplace’s Mitchell Hartman explains.

Mitchell Hartman: The number that pops out here is $12.6 million. That’s Romney’s 2010 capital gains income. It comes from investments, and is taxed at a lower rate than wages.

Victor Fleischer teaches tax law at the University of Colorado. He says most of Romney’s capital gains came from private equity investments he helped set up at Bain Capital more than a decade ago.

Victor Fleischer: A manager at Bain Capital will help advise the investment fund when they purchase portfolio companies, whether it’s Staples or Dunkin’ Donuts. When the fund ultimately sells those underlying investments, the partners at Bain take a share of the profits.

The profit may exceed 20 percent, but it may not pan out for years — until Staples or Dunkin’ Donuts has been turned into a profit-making machine and sold off.

There’s another reason Romney’s still making millions. He negotiated a sweet departure deal, under which he gets a cut of the profits from investments that Bain made after he left. Nice work, if you can get it — in retirement.

I’m Mitchell Hartman for Marketplace.