We have a severe housing shortage, and last week our mayor said that he’d help make matters worse.

If Eric Garcetti gets his way, rent control could be imposed on far more apartments in Los Angeles and throughout the state. That’d be great for the few folks lucky enough to get a rent-controlled unit. It’d be bad for everybody else.

That’s not a surprising statement. Studies have shown that. Let’s look at one of the latest.

A working paper published in January by the National Bureau of Economic Research examined the effect of a 1994 ballot initiative in San Francisco that slapped rent control on smaller buildings constructed before 1980. Three economists followed what happened to those buildings and compared their fate to similar buildings constructed after 1980.

So what happened? First, there was a reduction in the number of rent-controlled units as landlords decided to convert their buildings to condos or otherwise redevelop their properties. In fact, rent-controlled buildings were 10 percent more likely than the non-rent-controlled buildings to convert, “representing a substantial reduction in the supply of rental housing,” the report said.

Second, there was a 25 percent reduction in the number of renters living in rent-controlled units compared to 1994, largely because of “landlords demolishing their old housing and building new rental housing,” the study said. “New construction is exempt from rent control.”

So there was a drop in the number of rental units as well as a decrease in the number of tenants who enjoyed rent control. No surprise there.

In short, rent control makes matters worse, which pretty much every informed person knows with the apparent exception of Garcetti. What was a teeny bit more surprising was the working paper’s assertion that rent control increased gentrification as well as worsened income inequality in the city.

One of the authors of the working paper, Rebecca Diamond, an assistant professor of economics at Stanford University, was quoted as saying that rent control “pushed landlords to supply owner-occupied housing and new housing – both of which are really the types of housing consumed by rich people,” she said.

“So we’re creating a policy that tells landlords, ‘It’s much more profitable to cater to high-income housing taste than low-income housing tastes.’”

In other words, rent control makes matters much worse.

What’s particularly alarming about last week’s news is that the current move to impose more rent control would make matters even worse than you might expect. That’s because the proposed statewide ballot initiative that would roll back the Costa-Hawkins Rental Control Act (the initiative which Garcetti last week called a news conference to endorse), would not only give cities the green light to allow rent control to be slapped on apartments built after 1978, but it would take the extra step of limiting the ability of landlords to raise rents after one tenant leaves. The way it works now is that when one tenant leaves a rent-controlled unit, the rent can immediately catch up to market rates for the incoming tenant. Rent increases are limited thereafter, until that tenant leaves.

That provision alone is a killer. It would mean landlords would be doomed to falling further and further behind market rates. That means more apartment buildings would not pencil out, and landlords would rush to empty out their buildings, scrape the ground and construct something new – something that’s not an apartment building. We’d see declines much greater than 25 percent in tenants enjoying rent control.

Look, the yearning to do something is understandable. After all, rents have popped up alarmingly and even folks with good incomes are being priced out of homes. But imposing more rent control would only choke supply and make matters much worse.

The real issue is supply. If we had more construction, the shortage would eventually disappear. But for that to happen, developers need to feel confident that they can build with the certainty that they can earn enough income to pay their mortgage and other bills and get a reasonable return. Right now, they can’t. And mayoral endorsements of rent control make matters worse.

Charles Crumpley is editor and publisher of the Business Journal. He can be reached at ccrumpley@sfvbj.com.