Staged implementation of inclusionary zoning as a mechanism to improve housing affordability in Auckland, New Zealand

Abstract

Purpose The purpose of this paper is to analyse how the staged implementation of inclusionary zoning (IZ) performs relative to conventional IZ programmes in terms of increasing the number of low- and moderate-income households become homeowners. Design/methodology/approach The paper applies a matching model implemented through a mixed-integer programme model taking Auckland (New Zealand) housing market as a case study. The IZ is simulated by two features: a target price (below which affordable houses are defined) and the income threshold (below which any household gains access to the programme). The staging of IZ consists of first directing affordable houses to low-income households, where those houses that are not sold are cascaded to subsequent population groups with higher incomes. Findings The staged implementation of IZ does not necessarily imply that the number of sales will increase both for affordable and market-rate houses. However, a hybrid approach defined by two target prices results in a greater number of sales relative to a conventional IZ and a baseline affordable market while achieving market efficiency and equity. Research limitations/implications The paper is limited to the marginal impact of new affordable houses entering the market. It does not address further market rounds for houses left empty for tractability purposes. Also, the analysis is circumscribed to current renters and not owners, if owners were included they would outbid renters and distort the intended impact of IZ as an affordable housing policy. Originality/value The paper has relevance for policymakers because it provides evidence about the dimensions of IZ to have a lasting effect on housing affordability. The model is applied to a single housing market but is suitable to be generalized and adapted to a different urban environment.