Agency mortgage-backed securities (MBS) issued by Fannie Mae and Freddie Mac have historically traded in separate forward markets. We study the consequences of this fragmentation, showing that market liquidity endogenously concentrated in Fannie Mae MBS, leading to higher issuance and trading...

Measured as yield spreads against AAA corporate bonds, the convenience premium of agency MBS averages 47 basis points over 1995 - 2021, about half of the long-term-Treasury convenience premium. Both MBS convenience premium and issuance amount depend on mortgage rate negatively, consistent with a...