Republican front-runner Mitt Romney is finally caving to repeated demands, admitting he pays a 15% "effective" tax rate. An effective tax rate is the rate an indiviual would be taxed if taxing was done at a constant rate rather than a progressive rate.

Romney, under pressure from his Republican rivals who have questioned how the conservative made his fortune, made the announcement today and said he will release his tax returns in April around the federal tax deadline, according to the Associated Press.

However, he may only release his 2011 tax return and not those from previous years.

The former governor of Massachusetts told reporters in South Carolina today that the majority of his earnings are from investments, according to CNN reports. Both Newt Gingrich and Texas Governor Rick Perry are urging Romney to release his tax returns so Americans can get some insight into the Romney fortune.

A New York Times editorial, meanwhile, made the same appeal today calling Romney’s "insistence on secrecy impossible to defend now that he appears to be closing in on the nomination and questions have intensified about his personal finances and record as a venture capitalist.”

Romney is estimated to have a net worth as high as $270 million, according to Reuters.

Fifteen percent is the top federal tax rate for income that comes from investments.