During a period of tough competition between mortgage lenders for revenue and market share, and when the supply of creditworthy borrowers was limited, mortgage lenders relaxed underwriting standards and originated riskier mortgages to less creditworthy borrowers. In the view of some analysts, the relatively conservative government-sponsored enterprises (GSEs) policed mortgage originators and maintained relatively high underwriting standards prior to 2003. However, as market power shifted from securitizers to originators and as intense competition from private securitizers undermined GSE power, mortgage standards declined and risky loans proliferated. The worst loans were originated in 2004–2007, the years of the most intense competition between securitizers and the lowest market share for the GSEs.

What caused mortgage lenders to relax underwriting standards and approve riskier mortgages?