Although some Wall Street traders of Fannie Mae and Freddie Mac mortgage-backed securities are continuing to complain that the GSEs are using inside information to “cherry pick” the best MBSs for their own investment portfolios, available data sheds relatively little light on the subject. If the GSEs were in fact selecting the most desirable MBSs for themselves, one would expect to see lower or slower prepayment rates on their own retained portfolios than on the