Inclusionary zoning (IZ), also known as inclusionary housing, has become a popular policy tool that local jurisdictions use to increase the production of affordable housing. IZ ordinances either require or encourage builders of new residential developments to set aside a certain percentage of the housing units for low- or moderate-income residents. A key observation is that, although inclusionary zoning has increased the supply of affordable housing units in these two sites, IZ requirements must be clear and administered consistently so that developers can effectively predict when it is economically feasible to build projects that require inclusionary housing units.