A whole generation of young workers are being priced out of renting (let alone, buying) in major cities. Parking deserves part of the blame, suggests a recent study. Since the 1940s, many US cities introduced minimum parking rules: for every new unit of housing, developers must also build a certain number of parking spaces. This has effectively tied housing prices to transport costs.

But parking should be thought of as an equity issue, argues researchers Gregory Pierce and C.J. Gabbe in the journal Housing Policy Debate, Why? The average price of building a garage parking space (as much as $34,000 in 2012) is passed on to people whether they own a car or not, and distort the true demand for urban parking. “The lack of rental housing without bundled parking imposes a steep cost on carless renters—commonly the lowest income households—who may be paying for parking that they do not need or want,” write the authors.

To find out that price, the two urban environment researchers analyzed the 2011 National American Housing Survey data of the US Census. They found that about 16% of a housing unit’s monthly rental cost is attributable to the expense of building an urban parking spot. For the average renter that amounts to to $1,700 per year, or $142 per month.

Parking mandates increase housing prices by displacing area that could have gone to housing (thus shrinking supply), and makes each new unit more expensive to pay for more garage parking. A separate study in Los Angeles found the city’s parking minimums raised apartment prices by about $200 per month and price of a condo by about $43,000. Renters without cars end up subsidizing this arrangement to the tune of about $440 million annually in the US. While only 7% of US rental households lack cars, according to Census data, this burden falls most heavily on the urban poor since lower-income households can least afford to subsidize garage parking spaces.

It may be time to let the market decide. Private vehicle parking spaces can be priced and sold separately from housing. Urban planners are starting to advocate for new uses of city-owned street parking (such as San Francisco’s parklets), as well as loosening the connection between cars and housing. Researchers find that pairing the two inadvertently subsidizes (and increases) vehicle ownership. One researcher called such rules “a a fertility drug for cars.”

“The provision of parking supply without associated demand can only be characterized as wasteful,” writes Gabbe and Pierce. “While many households might have chosen to pay for on-site parking in a free market, this proportion is surely lower than what has been mandated.”

Some cities are starting to allow unbundled parking (a trend only likely to grow as ride-sharing and autonomous vehicles come to more cities). But there is resistance. A-P Hurd, a developer at Touchstone in Seattle, writes that residents in low-density areas can pass planning rules (such as minimum number of parking spaces) to block new construction, a concern more about neighbors’ desire to keep out new arrivals than residents’ mobility.