WASHINGTON -(Dow Jones)- The U.S. Federal Reserve released a staff study Monday saying the federal subsidies bestowed on government-chartered companies Fannie Mae (NYSE:FNM - News) and Freddie Mac (NYSE:FRE - News) are far higher than any previous estimates and the two do little to increase homebuying, lowering mortgage costs by just a fraction of previous estimates. "Fannie Mae's and Freddie Mac's ambiguous relationship to the government imparts an implicit subsidy to GSE shareholders and homeowners," the study reads, placing a dollar value on that relationship at between $119 billion and $ 164 billion. The report, prepared by staff economist Wayne...