>But, since 2008, vacancies have been declining steeply.
is missing one. It looks like this statement is based on his estimates. So... original research. I'll leave it to an actual statistician to analyze his methodology, but that statement doesn't jive with my experience.
I continue to suspect that the "housing shortage" (similar to the "labor shortage") is due to a mismatch between the value that industry expects and what are actually the rates necessary to support the population. Powerful institutions representing wealthy individuals and groups, and large swathes of people, like the status quo; it is, in fact, fundamental to their lifestyle, their finances, the overall economy, and they will (and have) done everything they can to keep prices and the perception of scarcity high. The situation doesn't seem rational from an inventory/demand standpoint because it isn't; there are enough house, and they should be worth less and more affordable. But we won't return to reality until the privileging of incumbents ends.