Unlike nearly every other presidential candidate, Republican Mitt Romney refuses to make public more than two years of tax returns. Today, the multimillionaire said he has paid a tax rate of at least 13 percent on his income in each of the past 10 years—but he still won't release his returns. Meanwhile, President Obama's returns have long been public and show he pays a 20 percent tax rate.

At a measly 13 percent, Romney, who is worth a quarter of a billion dollars, is paying significantly less in taxes than other high-income earners who pay 35 percent. Through the use of offshore tax shelters and other means, Romney pays a smaller tax rate than average taxpayers like nurses, firefighters and construction workers.

In more than three decades, no other nominees for either party—except Sen. John McCain (R-Ariz.)—have released fewer than five years’ worth of returns. Romney’s own father released a dozen years’ worth when he ran for the Republican presidential nomination in 1968.

What's Mr. 1% trying to hide?

Is Romney refusing to release his tax returns because:

• He didn't pay taxes in some years?
• He took huge advantage of tax breaks to outsource good U.S. jobs?
• He sheltered even more money than we're aware of in offshore Swiss bank accounts?

Or something else?

Tell us what you think Romney is hiding. Log in and comment below.