Housing growth drops 20 percent, on average, in cities making the sort of switch proposed by Portland’s Commissioner Mapps.

A new 11th-hour idea for rewriting the rules of Portland’s city government has several possible flaws, but here’s one: statistically speaking, it’d be likely to worsen the city’s housing shortage.

The proposal was publicly floated in a media interview three weeks ago by its loudest advocate, city Commissioner Mingus Mapps. Mapps’s idea, according to The Oregonian/OregonLive: to scrap the concept hammered out by a city-appointed citizen commission over the last year, a form of proportional representation, in favor of a winner-take-all system that would elect its entire council from smaller, one-winner districts.

A referendum that would implement proportional representation and other changes is on the November ballot in Cascadia’s third-largest city as measure 26-228. Mapps’s concept has yet to be fully hammered out and might yet change.

If Mapps’s proposal ends up as described by The Oregonian and wins support from other councilors and the public, Portland would be imitating a form of government that reduces housing growth in US cities by an average of 20 percent.

“The number of units permitted falls sharply . . . immediately upon the reform’s approval,”

wrote Evan Mast, the author of an academic paper on this subject circulated in 2020 and published in May, “Warding Off Development: Local Control, Housing Supply, and NIMBYs.”

ONE PORTLAND CITY COUNCILOR SAYS HE WANTS A COUNCIL ELECTED FROM SINGLE-WINNER WARDS

Here’s the current political situation in Portland: In late 2020, its city council named 20 people to research and propose changes to Portland’s charter—essentially its city constitution. This summer (2022), after much testimony and debate, those 20 people (the Charter Commission) proposed some changes to how the city’s government operates and how voters elect its officials. By a 17–3 vote, they sent this package directly to Portland voters’ November ballots, bypassing any edits from City Council.

The new election system they proposed was modeled on a system that’s common around the world: proportional representation. It would divide the city into four relatively large districts, each of which would use multi-winner ranked choice voting to elect three commissioners in rough proportion to the various political opinions and interests that make up each district. If more than one-quarter of a district ranks a candidate highly, that candidate earns one of the three seats in that district.

During an informational presentation from the Charter Commission, three city council members announced that though they liked the proposed changes to how the city is run, they had concerns about that sort of election system. Then, on Aug. 30, one of those council members, Mingus Mapps, announced that if November’s ballot measure fails, he expects to propose his own, different election system, one more familiar to many Americans: eight smaller districts that would each elect just one person.

It’s that system—a council made up entirely of “winner-take-all” wards—that a growing body of research says tends to lead to fewer homes being built.

ONE-WINNER WARD SYSTEMS SEEM TO CAUSE HOUSING SLOWDOWNS

One recent academic paper with this finding is from Evan Mast, a housing economist at the University of Notre Dame. He looked at housing growth rates in 238 cities that recently made the sort of switch that Mapps is suddenly advocating for in Portland: from at-large to district elections. It turned out that these cities generally saw a sharp dip in new construction immediately after their change. Then, after about two years, they tended to rebound somewhat to a new, lower equilibrium of housing production. Cities that switched to single-winner districts settled at about 20 percent fewer new permitted units per resident than cities that continued using at-large elections.

Another relevant paper is by two political scientists. Mich...