Hawaii proponents of YIMBY, a housing movement whose mantra is “yes in my backyard,” are poised for their first major win: the de facto elimination of single-family zoning across Hawaii. Bills are winding through the Legislature that would allow at least four units on every lot in the urban land district, a process called upzoning.

Supporters are quite clear about what they think they’re getting. Testimony from the Grassroot Institute, Housing Hawaii’s Future, Hawaii Appleseed, the NAIOP (a commercial real estate development association), Hawaii Gas, the state Land Use Commission and many more explicitly link this measure to affordable housing.

There are two paths advocates see for how this all works. It will, they believe, drive an increase in supply, which will drive down prices. These units are also, because of reduced lot sizes, de facto cheaper.

Many advocates point to Minneapolis as proof of how this works. Announced in 2018 and implemented fully in 2020, Minneapolis allowed, much like Hawaii’s Senate Bill 3202, up to three unit “plexes” on every residentially zoned lot in the city. This, according to some private market data, led to a reduction in inflation adjusted rents even as the rest of the country saw sharp increases.

But this tale is doubtful, if not downright false. Attributing Minneapolis’ construction to newly legalized plexes is like attributing a flood to a raindrop: homes of this sort make up only 1%-2% of the new homes permitted annually since 2018.

This is half as many plexes as Minneapolis constructed during 2000-2005, a period before the beneficent YIMBY reforms.

More fundamentally, it’s not clear that Minneapolis’ recent reforms have reduced rents. While some data-sets from apartment rental websites indicate flat rents, the gold-standard data collected by the Census indicates that real gross rents have actually climbed by 8% or so since 2017.

In this regard, Minneapolis is worse than neighboring St. Paul, which did not upzone, worse than Honolulu, and even worse than that least-affordable of cities, San Francisco.

That upzoning may have not actually done much in Minneapolis is a point that some YIMBYs are coming around to: Reason magazine recently declared that “Eliminating Single-Family Zoning Isn’t the Reason Minneapolis Is a YIMBY Success Story.”

So what impact would upzoning have on Hawaii’s affordability? Well, at least on Oahu, we shouldn’t expect much.

In all probability, redeveloping existing lots into plexes or townhomes will result in homes costing more than a family at 140% of AMI (area median income) could afford. New townhomes at Koa Ridge start in the low $600,000 and they’ve been built on cheaper agricultural lands. Developing urban lots may well cost more.

Urban land isn’t just more expensive, it will get more expensive — studies have shown upzoning leads to prices increases for eligible lots between 5% and 20%.

None of this makes upzoning bad policy. It is good policy to allow cities to grow efficiently. And something needs doing about the constant naysaying that so often torpedoes much-needed housing.

But upzoning is decidedly not affordable housing policy. The politicians making hay over affordable housing, from the governor’s mansion to the Legislature and City Council — owe us affordable housing policy. Upzoning, despite its merits, is not that.

Makana Hicks, an engineer from Pupukea, is a member of the Hawaiian Civic Clubs and a policy organizer with Democracy Policy Network.