The Federal Reserve said on Wednesday that bigger U.S. banks would have an extra year to calculate a capital requirement known as the supplementary leverage ratio for stress testing. Institutions subjected to the leverage ratio requirement will have to show regulators what the ratio would be in a stressed scenario beginning in 2017. The extension applies to banks with more than $50 billion of assets, of which there were 39 at the end of the third quarter, according to data from the Federal Deposit Insurance Corp.