A rule proposed late last month to impose margin requirements in the single-family “to-be-announced” market would draw in the multifamily housing finance programs of Fannie Mae and Ginnie Mae, according to industry trade groups. At issue is SR-FINRA-2015-036, a proposal to amend Financial Industry Regulatory Authority Rule 4210 margin requirements for TBA transactions, including adjustable-rate mortgage transactions, specified pool transactions, and transactions in collateralized mortgage obligations, issued in conformity with a program of an agency or government-sponsored enterprise, with forward settlement dates. In a letter last week to the Securities and Exchange Commission, more than a dozen industry groups expressed...