The U.S. budget deficit for this year is projected to come in far below what was estimated just a few months ago, a government study released Tuesday found. The Congressional Budget Office (CBO) cites higher tax revenues and better-than-expected rescue repayments by mortgage giants Fannie Mae and Freddie Mac as the key reasons for the improved outlook. The budget office now predicts a 2013 budget deficit of $642 billion, more than $200 billion below its February estimate. This year's shortfall would register at 4 percent of the economy, far less than the 10.1 percent experienced in 2009 when the government ran a record $1.4 trillion deficit. The deficit picture is expected to continue to improve next year and beyond, with the 2015 deficit now projected at $378 billion, just 2.1 percent of the economy. The budget office predicts deficits over the coming decade of $6.3 trillion, down $522 billion from earlier projections.