One of the most significant reasons that banks relaxed their lending criteria was their ability to transfer the risk of losses through securitization of loans (discussed below in additional detail), with Fannie Mae or Freddie Mac as the ultimate owner in a large fraction of securitized mortgages. Ryan (2008) cites several related reasons for the explosion in subprime loans, including the strategic switch of commercial banks to retail banking following the technology bust; the consistent increase in housing prices and expected continuation of low losses given default; low mortgage
interest rates that continued to decrease through 2003, which made housing affordable despite the market appreciation; reduced revenue from prime mortgages; declining credit spreads; and unprecedented liquidity in global markets that led investors to search for new high yield investment opportunities.