If you’ve ever been to a city council meeting, you know that people love to complain about a lack of parking. People want to be able to store their cars as close as humanly possible to the front door of whatever place they’re trying to visit. Such complaints create an artificial impression that parking is in short supply.

But according to a new report by the Research Institute for Housing America, an arm of the Mortgage Bankers Association, cities actually have an overabundance of parking space. They’re also very bad at estimating their real needs for parking spots. What’s worse, all the land being dedicated to cars is contributing to skyrocketing housing values that price lower-income renters and homebuyers out of the market.

The study, “Quantified Parking: Comprehensive Parking Inventories for Five U.S. Cities,” counted the parking spaces in five cities: New York City, Seattle, Philadelphia, the Iowan capital of Des Moines, and Jackson in Wyoming. The count is the first of its kind; according to the report, “comprehensive parking inventories have never existed for US cities.”

The study found that parking in the US represents billions of dollars worth of public and private investments. In New York City alone, parking is worth $20.6 billion and is controlled by a handful of companies.

The town of Jackson, Wyoming (pop. 10,000ish) has a 27:1 ratio of parking spaces to households, according to the report, and yet a decade ago spent $17 million on a parking structure that provides exclusively free parking.

“When a preconception of too little parking infects policymakers, more parking tends to get built and provided to everyone for free,” wrote Eric Scharnhorst, a principal data scientist at the startup Parkingmill and the study’s author.

Drivers in the US spend an average of 17 hours a year looking for the perfect parking spot, and most cars in the US are parked 95 percent of the time.

But scooping up valuable land for the purposes of car storage has the effect of driving up the cost of land designated for housing, according to experts around the world: it’s more lucrative to operate a parking structure than a housing unit. This is great for landowners who are looking to make a big return on their investments, but it makes real estate markets inhospitable to new home buyers and renters.

As the report noted (and as real estate sites confirm), the median home sale price in Jackson hovers around $1 million. According to a local real estate company, 2017 marked the town’s lowest real estate inventory in 30 years.

This dynamic played out in most of the cities studied in the report. Seattle’s got more than twice as much parking than it really needs, while Philly’s got nearly four parking spots for every home. Des Moines has 83,141 households, 217,000 people, and 1.6 million parking spots—that’s 19 spots per household.

Of all the cities profiled in the report, only New York City—the most densely populated city in the US—had a reasonable ratio of parking spots to households. “There are an average of 16.2 households per acre and 10.1 parking spaces per acre in New York,” Scharnhorst wrote.

In jam-packed cities with climbing rents, cities are going to be increasingly faced with a dilemma: parking or housing? Just this week in Silicon Valley, the city of Palo Alto—which, as the home to Google, Tesla, and many other tech companies, has one of the greatest concentrations of wealth in the world—voted to allow people living in RVs to park on city property. Meanwhile, a bill in San Francisco that would allow its transit operator to build housing on station properties is currently before the California legislature. (Don’t get too excited. California also recently shot down a bill that would have allowed for more residential construction near public transit.)

These are just stopgap measures, though. As suggested by the report, cities should do regular parking audits to diagnose current car-storage supplies and prescribe a more common-sense solution to a looming housing crisis.

What a lot of cities really need is to become more affordable—and that’s accomplished in part by maximizing land zoned for housing, as well as promoting public transit.