If an inclusionary housing ordinance is regarded as an “exaction”—because it compelled a developer to pay through land dedication or in-lieu fees—then the city must show that (1) there was a reasonable relationship between the deleterious effects of the new housing and the economic burden imposed on the developer —the nexus—and (2) the burden is reasonably proportional to the problems created by the development.
Bernhardt, Roger, "California Bldg. Indus. Ass'n. v. City of San Jose" (2015). Publications. 739.