To someone ignorant of economic reasoning, rent control seems like a great policy. It appears instantly to provide “affordable housing” to poor tenants, while the only apparent downside is a reduction in the income flowing to the fat-cat landlords, people who literally own buildings in major cities and who thus aren’t going to miss that money much. Who could object to such a policy?

First, we should define our terms. When a city government imposes rent control, it means the city makes it illegal for landlords to charge tenants rent above a ceiling price. Sometimes that price can vary, but only on specified factors. For the law to have any teeth — and for the politicians who passed it to curry favor with the public — the maximum rent-controlled price will be significantly lower than the free-market price.

The most obvious problem is that rent control immediately leads to a shortage of apartments, meaning that there are potential tenants who would love to move into a new place at the going (rent-controlled) rate, but they can’t find any vacancies. At a lower rental price, more tenants will try to rent apartment units, and at a higher rental price, landlords will try to rent out more apartment units. These two claims are specific instances of the law of demand and law of supply, respectively.

In an unhampered market, the equilibrium rental price occurs where supply equals demand, and the market rate for an apartment perfectly matches tenants with available units. If the government disrupts this equilibrium by setting a ceiling far below the market-clearing price, then it creates a shortage; that is, more people want to rent apartment units than landlords want to provide. If you’ve lived in a big city, you may have experienced firsthand how difficult it is to move into a new apartment; guides advise people to pay the high fee to a broker or even join a church because you have to “know somebody” to get a good deal. Rent control is why this pattern occurs. The difficulty isn’t due to apartments being a “big-ticket” item; new cars are expensive, too, but finding one doesn’t carry the stress of finding an apartment in Brooklyn. The difference is rent control.

Rent control reduces the supply of rental units through two different mechanisms. In the short run, where the physical number of apartment units is fixed, the imposition of rent control will reduce the quantity of units offered on the market. The owners will hold back some of the potential units, using them for storage or keeping them available for (say) out of town guests or kids returning from college for the summer. (If this sounds implausible, consider just how many people in a major city consider renting out spare bedrooms in their homes, as long as the price is right.)

In the long run, a permanent policy of rent control restricts the construction of new apartment buildings, because potential investors realize that their revenues on such projects will be artificially capped. Building a movie theater or shopping center is more attractive on the margin.

There are further, more insidious problems with rent control. With a long line of potential tenants eager to move in at the official ceiling price, landlords do not have much incentive to maintain the building. They don’t need to put on new coats of paint, change the light bulbs in the hallways, keep the elevator in working order, or get out of bed at 5:00 a.m. when a tenant complains that the water heater is busted. If there is a rash of robberies in and around the building, the owner won’t feel a financial motivation to install lights, cameras, buzz-in gates, a guard, or other (costly) measures to protect his customers. Furthermore, if a tenant falls behind on the rent, there is less incentive for the landlord to cut her some slack, because he knows he can replace her right away after eviction. In other words, all of the behavior we associate with the term “slumlord” is due to the government’s policy of rent control; it is not the “free market in action.”

In summary, if the goal is to provide affordable housing to lower-income tenants, rent control is a horrible policy. Rent control makes apartments cheaper for some tenants while making them infinitely expensive for others, because some people can no longer find a unit, period, even though they would have been able to at the higher, free-market rate. Furthermore, the people who remain in apartments — enjoying the lower rent —receive a much lower-quality product. Especially when left in place for decades, rent control leads to abusive landlords and can quite literally destroy large portions of a city’s housing.