Black Friday is nearly upon us! All good Americans are honor-bound to abandon their turkey-addled relatives, proceed to the nearest shopping district, and buy stuff. If you are a suburbanite, you are also obligated to spend time complaining about how hard it is to park at the mall, and sneer at the city stores without parking lots; if you are a city-dweller, your job is to ridicule suburbanites who can’t bear to be more than ten yards from their cars at any time. But what if suburbanites had their way? What if the city stores did all have parking lots right next door?

That is the question posed in a pair of recent study comparing parking in three cities in Massachusetts (Cambridge, Somerville, and Lowell) and four other small cities in the northeast and midwest. University of Connecticut researchers Christopher McCahill and Norman Garrick looked at how the supply of parking and driving behavior changed over time. Then, they checked on statistics for number of employees in the city, number of residents, and other measures of happy-city activity.

Locally, Cambridge and Somerville have kept auto use low by American standards. Fewer than 60% of Camberville’s residents commute by car, compared with 91% of Lowell’s work force. The cities also provide radically different amounts of parking. Cambridge and Somerville together commit less than 80 square feet for parking per resident/worker, while Lowell offers a spacious 171 square feet of parking for every resident and employee. Ah, the luxury of Lowell!

So what happens when you fill a city with convenient parking lots? Not much, according to McCahill and Garrick.

The cities with the most parking—and thus the most automobile use—also had the lowest amount of activity, measured by the number of residents plus employees per square mile. Since 1960, cities with the lowest levels of parking and automobile use added on average 3,500 employees per square mile: Cambridge added 7000 employees per square mile. By contrast, auto-dependent communities like Hartford and Lowell have lost jobs since 1960.

The problem, it seems, is that when you commit urban land to parking, you can’t use it for anything else. As this photo shows, cars take up a lot more space to transport people than buses or bicycles (or feet!). You can’t go shopping in a parking lot, or meet a friend for lunch there, or, stop to smell the flowers, because there aren’t any flowers. McCahill and Garrick write,  “This [loss of space to parking] will result in a lower number of total activities, unless the land use intensity increases. The lost activities typically relocate further out in the surrounding region, outside of the urban core.” Why go to a city if there isn’t anything to do there? You’d might as well go someplace where you can park.

Plenty of people are arguing with these ideas. Cambridge is special, they say, because of all the development around Kendall Square during the internet boom, and the city only stopped making new parking in 1985 because it was legally obligated to under the Clean Air Act (I can’t find direct confirmation of this idea, but the Cambridge Pedestrian Plan is full of good reasons why Cambridge should limit parking anyway.) But would Kendall Square have revived if the city had required acres of parking around the shiny new buildings? Or did it grow in magnificence because Cambridge already had a Kendall Square T-stop in place? (or was it the Miracle of Science that enticed investors?) You can find an exception, and explanation for every city—but the correlation between increased parking and loss of jobs, residents, and tax revenue is still there.

But my job here isn’t to lobby for multi-modal transport options. I write about parks which also take up space where people could live and work, as I discussed in this space a few months ago. But parks are supposed to be “third places” where people can meet and mingle with folks they wouldn’t otherwise encounter. And they’re pretty.

Organized park advocates spend a fair amount of time quantifying the economic impact of parks. Chicago’s mind-bogglingly successful Millennium Park is supposed to be contributing more than $100 million a year to the local economy via increased hotel revenues, retail sales and so on. The Massachusetts Turnpike Authority noted that real estate values of commercial next to the Rose Kennedy Greenway jumped by more than 577% between 1988 and 2005–but that jump may have partly been caused by relief that the Big Dig was finally over. The Trust for Public Land estimated that Bostonians got more than $354 million of use out of Boston parks in 2006… but having a nice time walking your dog doesn’t make new jobs. Or does it?

Parking lots are one type of public space; parks are another. Public toilets, T stations, homeless shelters, hospitals, schools, and highway interchanges all have an effect on the land around them–how it iss perceived, how it is used. The problem is judging what these public institutions do, and their value to the community.

McCahill and Garrick quote Hartford officials stating in 1972, “the most critical improvement to [neighborhood shopping districts] which could be made at this time is the provision of off-street parking facilities.” That improved off-street parking probably made life easier for the suburban commuters, and worse for the city, which lost jobs, residents, and tax revenue. I’m sure Hartford  got what it paid for. I don’t think it was worth it.