There is a growing debate about whether upzoning is an effective policy response to housing shortages and unaffordable housing. This paper provides empirical evidence to further inform debate by examining the various impacts of recently implemented zoning reforms on housing construction in Auckland, the largest metropolitan area in New Zealand. In 2016, the city upzoned approximately three quarters of its residential land to facilitate construction of more intensive housing. We use a quasi-experimental approach to analyze the short-run impacts of the reform on construction, allowing for potential shifts in construction from non-upzoned to upzoned areas (displacement effects) that would, if unaccounted for, lead to an overestimation of treatment effects. We find strong evidence that upzoning stimulated construction. Treatment effects remain statistically significant even under implausibly large displacement effects that would necessitate more than a four-fold increase in the trend rate of construction in control areas under the counterfactual of no-upzoning. Our findings support the argument that upzoning can stimulate housing supply and suggest that further work to identify factors that mediate the efficacy of upzoning in achieving wider objectives of the policy would assist policymakers in the design of zoning reforms in the future.

关于升级分区是否是应对住房短缺和负担不起的住房的有效政策反应的争论越来越多。本文通过研究最近实施的分区改革对新西兰最大的都市区奥克兰的住房建设的各种影响，提供了经验证据，以进一步为辩论提供信息。2016 年，该市对大约四分之三的住宅用地进行了升级分区，以促进更密集的住房建设。我们使用准实验方法来分析改革对建设的短期影响，考虑到建设从非升级区到升级区的潜在转变（位移效应），如果不加以考虑，将导致高估治疗效果。我们发现了强有力的证据表明升级分区刺激了建设。即使在令人难以置信的大位移效应下，处理效果在统计上仍然显着，在没有升级分区的反事实下，控制区域的建设趋势率需要增加四倍以上。我们的研究结果支持升级分区可以刺激住房供应的论点，并建议进一步开展工作以确定调节升级分区在实现更广泛的政策目标方面的功效的因素，这将有助于政策制定者设计未来的分区改革。