The Milken Institute said the GSEs’ duty-to-serve policy is more complicated than other affordable housing reform issues because it forces the secondary market to boost lending in the primary market and assumes those private firms are underperforming. The conservative think tank published a paper this week authored by Michael Stegman and Phillip Swagel on the role of duty-to-serve in which it examined the policy and its potential impact on the mortgage market. While DTS currently encompasses manufactured housing, rural housing and affordable housing preservation, Milken said housing finance reform debates have centered on creating a DTS that includes areas beyond those three targets.