Salim Furth

Salim Furth

Mumbai upzoning

A 2017 increase in allowed floor area ratio in Mumbai had a tremendous impact on affordability by accidentally improving the economics of smaller apartments.

Market Affordable

Check out my new post at Metropolitan Abundance Project: How “inclusionary” are market-rate rentals? In metropolitan Baltimore, a family of four making $73,000 in 2024 qualifies for 60% AMI affordable housing, where it would pay $1,825 per month for rent, utilities included. A third of new market-rate three-bedroom units in Baltimore are rented at around that level.Baltimore is typical, as it turns out. In most U.S. metro areas, a substantial share of rentals constructed since 2010 were, in 2021 and 2022, affordable at 60% of AMI… You can also check out maps showing rentals affordable at 80% and 120% of AMI. The ACS data don’t let me distinguish market-rate from subsidized rentals, so these include LIHTC and other subsidized rentals. Those, however, can’t explain away the core result, and the data don’t show the bifurcated market that some people imagine, with a huge gap between market and deed-restricted rents.

The urban economics of sprawl

Should YIMBYs support or oppose greenfield growth? Two basic values animate most YIMBYs: housing affordability and urbanism. Sprawl puts those values into tension. Let’s take as a given that sprawl is “bad” urbanism, mediocre at best. Realistically, it’s rarely going to be transit-oriented, highly walkable, or architecturally profound. So the question is whether outward, greenfield growth is necessary to achieve affordability. And the answer from urban economics is yes. You can’t get far in making a city affordable without letting it grow outward. Model 1: All hands on deck Let’s start with a nonspatial model where people demand housing space and it’s provided by both existing and new housing. Existing housing doesn’t easily disappear, so the supply curve is kinked. A citywide supply curve is the sum of a million little property-level supply curves. We can split it into two groups: infill and greenfield, which we add horizontally. If demand rises to the new purple line, you can see that the equilibrium point where both infill & greenfield are active is at a lower price & higher quantity than the infill-only line. The only way to get some infill growth to replace some greenfield growth, in this model, is to raise the overall price level. And even then, the replacement is less than 1-for-1. Of course, this is just a core YIMBY idea reversed! In most U.S. cities, greenfield growth has been allowed and infill growth sharply constrained, so that prices are higher, total growth is lower, and greenfield growth is higher than if infill were also allowed. At the most basic level, greenfield growth is simply one of the ways to meet demand. With fewer pumps working, you’ll drain less of the flood. Model 2: Paying for what you demolish Now let’s look at a spatial model where people […]

And the Oscar for best paper goes to…

A friend asked what are the best papers supporting land use liberalization. That’s a broad question, but here are some of my answers. Affordability The basic case for zoning reform, across the political spectrum, is that the rent is too damn high. Michael Manville, Michael Lens, and Paavo Monkkonen give a combative and accessible review of the evidence in their Urban Studies paper (2020). The principal drawback is that it is rapidly becoming dated, as evidence and research come in from more recent reforms. The most important of those may be Auckland’s, which Ryan Greenaway-McGrevy has reported in a few papers, including this Economic Policy Center working paper (2023). Using a synthetic control method (which is not perfect, to be sure), Greenaway-McGrevy finds that upzoned areas had 21 to 33 percentage points less rent growth. A new candidate for the best review of the evidence on zoning reform and affordability is Vicki Been, Ingrid Gould Ellen, and Katherine M. O’Regan’s late 2023 working paper, “Supply Skepticism Revisited.” Racial integration Many authors from different disciplines have shown that both the intent and effect of zoning as practiced in the U.S. were racist and classist. That is, zoning policies have separated people by race, homeownership status, and income more than would have occurred in an unregulated market. Allison Shertzer, Tate Twinam, and Randall Walsh’s review of the evidence in Regional Science and Urban Economics (2022) is concise and helpful. However, fewer authors have attempted to show that removing specific zoning restrictions reduces existing patterns of segregation. One is Edward Goetz, in Urban Affairs Review (2021). He makes a qualitative argument. I’m unaware of a good causal, quantitative paper showing how broad upzoning impacts local integration (but I would happily commission it if anyone wants to write it!) Environment & climate Along some […]