"There are two huge holes in the textbook argument.  The first is that it overlooks neighborhood effects—literally.  The most compelling argument for rent control is neighborhood stabilization, the idea that social capital in an urban environment requires stable residence patterns.  If prices are volatile, and this leads to a lot of residential turnover, the result can be a less desirable neighborhood for everyone.  Thus the quality-adjusted supply curve is partly a function of price (or at least price stability in a dynamic model), and the S and D curves are not independent of each other.  You’ll notice that not a single textbook treatment of rent control mentions stabilization as an objective, even though this is a standard element in the real-world rhetoric surrounding this issue.  Again, I’m not taking a position, just saying that the representation you get at the introductory level is an ideological construct, not an honest analysis.

"The second hole is that rent control ordinances are normally replete with measures intended to maintain supply incentives, like price increases tied to investment in housing quality or simply spreading out increases over a longer time so tenants are able to adjust.  Again, these measures may succeed or fail, but a simple horizontal line in a one-period S&D model doesn’t begin to address them.

"In fact, advocates for rent control have taken Econ 101 (most of them), but they just disagree on how large the positive and negative impacts are. The purpose of economics should be to help us think clearly about the matter—for instance by identifying the potential empirical data that could adjudicate between competing arguments—but in its textbook form it is a ritualistic way of curtailing thought."