Housing Constraints and Spatial Misallocation: Comment
评论了Hsieh和Moretti（2019）关于放松三个美国城市土地利用监管可提高GDP 3.7%的研究，发现其代码错误导致结果偏差，且模型结果依赖于人口单位的任意选择；修正后效果比原报告小两个数量级。
Hsieh and Moretti (2019) find that relaxing land use regulations in three productive US cities would increase GDP by 3.7 percent. In this comment, I revisit their findings. I first attempt to replicate their result and find that their counterfactual would lower output. I document errors in their code that explain this discrepancy. I next show that the results of their model depend on the arbitrary choice of population unit. I propose a modification to their model that eliminates unit dependence. Their experiment raises output in the modified model, but the effect is two orders of magnitude smaller than what they report.