Are All Ratings Created Equal? The Impact of Issuer Size on the Pricing of Mortgage-Backed Securities

Initial yields on both AAA-rated and non-AAA rated mortgage-backed security (MBS) tranches sold by large issuers are higher than yields on similar tranches sold by small issuers during the market boom years of 2004-2006. Moreover, the prices of MBS sold by large issuers drop more than those sold by small issuers, and the differences are concentrated among tranches issued during 2004-2006. These patterns suggest that investors priced the risk that large issuers received more inflated ratings than small issuers, especially during booming periods