David Cay Johnston wonders if Mitt Romney’s decision to release his tax returns will increase the controversy surrounding his years at Bain Capital, in his column, “The Burden Of Romney’s Tax Returns:”

A tax return says a lot about a man, especially one aspiring to be president.

If Mitt Romney makes good on his promise during Thursday night’s Republican candidates’ debate to release “multiple years” of his returns, it will likely stir up rather than calm the political storm unless he makes public all of his returns from 1984 through 1999. Those are the years when he built a fortune of more than $200 million while running Bain Capital Management.

There’s no suspicion that Romney has done anything illegal. But what should be secret about the taxpaying relationship between a presidential hopeful and his government?

Romney himself said late on Thursday: “I’m not going to apologize for being successful.”

The former Massachusetts governor disclosed this week that he pays about 15 percent of his income in federal income taxes. That’s the same effective tax rate as a single wage earner making $60,000. Most of Romney’s income consists of dividends and capital gains, which Congress taxes at 15 percent. Were his income in wages, he would have paid a much higher rate.

Congress requires that most workers have income taxes withheld from their pay, but not so investment partnership managers like Romney, who cofounded Bain Capital Management and ran it for 15 years. They can earn compensation now and pay taxes later, decades later if they want. It’s called “carried interest.”

At the debate Romney wouldn’t say just how many years of returns he would make public. He has yet to share any of them. Before Thursday night, he had spoken only of releasing returns come April, the 2011 tax deadline. He came under public pressure to deliver more.