They're not saying that "construction of public housing or financial support for private investors engaged in social housing development" is not beneficial. Th

They're not saying that "construction of public housing or financial support for private investors engaged in social housing development" is not beneficial. They're saying that the "null hypothesis" of "mainstream chicago-school economics" would be: 1. The above laws would be beneficial to construction of low-income housing 2. rent control would be detrimental to construction of low-income housing When some of the laws did both at once, it is hard to disentangle the effects, and the study is calling out that the confounding variable of the aforecited amendments to rent control laws is not well controlled for, calling into question the overall conclusions.