 Diamond has made fundamental contributions to a variety of areas, including government debt and capital accumulation, capital markets and risk sharing, optimal taxation, search and matching in labor markets, and social insurance.Diamond (1965) extended the Ramsey–Cass–Koopmans model, from a representative infinitely-lived agent to a setup where new individuals are continually being born and old individuals are continually dying.He built on a framework developed by Paul Samuelson, who had termed it "an exact consumption-loan model."