The DC Council is strongly considering legislation that would create the most generous paid parental leave policy in the nation, a popular proposal that also will cost a lot of money. Those costs are something the council has to explicitly consider when contemplating the creation of a new spending program.

But when a handful of concerned citizens got the city to ban new construction in the Lanier Heights neighborhood, there was no explicit consideration of costs.

A change to the zoning code was a freebie that the political system could grant to the people upset about the idea of denser construction without taking anything away from anyone.

Except in the real world, restrictions on construction clearly do have a cost. They result in less construction employment, lower population, and a smaller tax base and impact the availability of houses and workers throughout the region. But the way American cities do business, these kinds of costs simply aren't considered when zoning rules are made, meaning there's no check on indulging the regulatory whims of anti-development busybodies.

Mark Farrell, a member of San Francisco's Board of Supervisors (i.e., city council), wants to change that and is forcing the city's chief economist to conduct an unprecedented economic impact study of the city's various land use and development rules.

Facts could restart the urban growth machine

In an influential 1976 paper, Harvey Molotch wrote of "The City as Growth Machine," explaining that a powerful coalition of real estate interests, building trade unions, and public sector workers controlled urban politics and pushed it on a trajectory to ever more building.

Actual experience shows this is not the case. While Molotch's growth machine coalition does tend to mobilize around a handful of high-profile projects — often stadiums, convention centers, or redevelopment schemes focused on waterfront industrial areas — the vast majority of land use decisions go the other way. Instead of a growth machine, cities see a series of decisions made on a local basis generally in response to very parochial concerns about street parking and "neighborhood character" that completely ignore citywide economic impact.

Yale University legal scholar David Schleicher argues that urban growth machines fail because big-city politics in the United States lacks the element of partisan competition that forces elected officials to articulate a citywide vision. Practical political competition happens on a purely local, purely idiosyncratic level, so politicians respond to purely local, purely idiosyncratic concerns.

There's nothing an individual city council member can do about this dynamic, but Farrell's initiative tackles it from another direction. Current urban practice doesn't give elected officials any basis on which to evaluate land use decisions in a citywide context. Decisions made in one neighborhood clearly do have implications for people who live elsewhere, but those implications aren't counted and clarified anywhere. Proposals for citywide changes have obvious local costs to people who don't like the status quo, but there's no way to discuss the subtler — but ultimately more important — broader citywide benefits.

Politicians are noticing the urban housing crisis

Farrell's initiative in San Francisco is also significant simply because it's an example of a nascent trend of big-city elected officials taking note of a growing body of scholarship on the malign influence of anti-density rules in America's coastal cities.

Farrell's statement on his initiative discusses this explicitly and sees the forthcoming report as part of contributing to this new body of conventional wisdom:

The discussion around the impacts of zoning and land-use regulations, especially in coastal cities, has started in earnest as research and studies have been released from economists at University of California Berkeley, the University of Chicago, and from the Chairman of the Council of Economic Advisors for the White House. Early research and studies suggest that overly restrictive zoning and land-use regulations do have far-reaching impacts on housing costs, economic inequality, mobility, and productivity.

Kevin Honan, who represents parts of Boston in the Massachusetts assembly, is championing legislation that would force Boston-area cities and towns to change zoning to allow for infill development. New York City Mayor Bill de Blasio pushed a major citywide zoning overhaul that should allow for more construction. California's official Legislative Analyst's Office has analyzed the state's housing affordability crisis as largely a product of overly restrictive zoning.

So far, none of this has yet amounted to major policy change (though the New York rezoning is important), but it does signal that housing supply is on the policy agenda in a way that simply wasn't the case a few years ago. Farrell's initiative may or may not make a difference in San Francisco, but it represents another sign of growing momentum for change.

220 years of population shifts in one map