Developer obligations (Dos) in the US are based on indirect rationales, as can be expected in a country with a long tradition of strong private property protections. The applications of DOs vary widely, as localities often have large legislative powers to regulate them. In England, Negotiable DOs (NDOs) increased in popularity since the 1970s because they seemed to obtain larger contributions than the statutory non-NDOs and because of the public policies in the 1980s towards public-private partnership in urban development. DOs supported on an indirect rationale: contributions focused thus on the infrastructure needed for the development. Developer obligations have a long history in Canada. Formal DOs have been used in all provinces, and informal DOs even longer. Since the 1960s, DOs in Korea have been part of land readjustment mechanisms which used to be the dominant land management strategy in the country.