Federal regulators are aiming for a delicate balance in new securitization rules that will nudge the mortgage industry toward new non-agency MBS issuance, including making sure there is enough collateral to provide a sustainable volume of new deals. The Government Accountability Office this week released a new report on the impact of the Dodd-Frank Act on the residential mortgage market, confirming the analysis by federal regulators that the proposed risk-retention rule would leave a significant share of the mortgage market outside the qualified residential mortgage definition. The GAO said that about 80 percent of ... [includes two data charts]