The sense of crisis around housing affordability in many of America's cities is at the highest level it's been in a long time. Responses to the crisis are often politically contentious, but the existence of a crisis is no longer so. And policy makers have been marshaling quantitative studies to make the case for their preferred reforms, leading to a barrage of headlines such as:

Numbers are a good rallying cry. Numbers are a measurable goal that can inform concrete action. They're useful.

But numbers also simplify. They create the temptation to become fixated on the number itself and lose sight of context. They cause us to fixate on outcomes and forget process.

The Process Matters

At Strong Towns, we're all about process. In the tradition of urban thinkers such as Jane Jacobs, we think that how our cities are planned, financed, and built is more important to get right than knowing the type of city that will ultimately emerge. And yet that's hard to reconcile with the urgency with which people, justifiably, talk about housing affordability, which leads to proposals like these:

"Ban zoning statewide." "Abolish all height limits. Allow only 50-plus-story towers near transit stations." "Just build it all as social housing." "Use all vacant land owned by local government for high-rise affordable housing."

These are all things I've heard advocated in earnest by well-meaning housing advocates. In other words, just get the units built. Who cares how they're distributed or who builds them? Just make it happen! We need them!

The world looks simple when you optimize for one variable. And yet, anyone familiar with the history of North American cities (or, almost certainly, even just their own city) can cite examples of grave harm done by this sort of tunnel vision.

Optimize for the goal of removing visible blight? You get the bulldozers of urban renewal.

Optimize for the goal of providing public housing as cheaply and politically-uncontroversially as possible? You get horror stories like Pruitt-Igoe.

Optimize for the goal of moving traffic at high speed, despite the risks? You get statistically inevitable tragedy.

Our decisions have fallout. Optimize housing policy simply to increase the number of homes, and there's no question that we'll make decisions with the potential to radically transform a place's physical and social fabric in a short amount of time. And that they will have fallout too.

And yet, those numbers.

A common form of pushback we get at Strong Towns when we talk about incremental development as a process is that it's not up to the scope of the challenges our cities face. That, by asserting that cities are complex systems and we should tread lightly in disrupting them through top-down action, we're not taking the affordability crisis seriously. (Or climate change seriously. Or car dependence seriously. Et cetera.)

We've praised Minneapolis's plan to allow the next increment of development—duplexes and triplexes—in all single-family areas citywide. We've spoken positively of similar moves in Vancouver and urged strongly that Austin, TX follow those cities' leads. This kind of policy is a huge step toward re-legalizing the incremental, organic evolution of the city, and addressing housing affordability and ecological challenges as an additional plus.

But there's a segment of our audience that's unsatisfied: It's not enough. We can't stop at triplexes: we need larger buildings too. We need X number of units to deal with our affordability problem. We need X amount of density to make transit viable, or to make places financially productive. This triplex thing is small potatoes: it's good news, sure, but it's not up to the task of transforming our cities in the way that's necessary.

There are extreme versions of this argument out there, but I think an eminently fair and reasonable version is that made by Joe Cortright of City Observatory (a Strong Towns member and longtime friend of ours) in his essay "You're Going to Need a Bigger Boat." The whole thing is worth reading, but here are some representative excerpts:

Legalizing accessory dwelling units, duplexes, triplexes and fourplexes does hold the promise of adding to affordability while injecting some very “gentle density” into single family neighborhoods. But it is far from up to meeting the scale of our housing affordability problems. For that, we need to build larger multi-family buildings, including apartments. The “Russell” [ed: a 68-unit apartment building in Portland that Cortright uses as a case study] avoids about 20 demolitions of single family homes. The “Russell” has a bigger impact on adjacent properties than the a single row house project, but you’d need 20 more row house projects, somewhere, to provide as much housing as the Russell.... There’s a good argument to be made that we’re underbuilding density in many locations where it makes sense. Neighborhoods with great transit, a mix of commercial uses, and high levels of walkability may justify more than just a duplex or triplex on a particular site. We ought to be think about the long term, what the demand for the neighborhood is likely to be in 2050 or even 2075, rather than in terms of the 20 year time horizon of most housing affordability analyses.

For the sake of this post, I don't want to get into the weeds of quantifying "need." Let's say Cortright is correct (and I agree that he is) that a place with the kind of pent-up demand and affordability issues that Portland faces needs a lot more new housing units than a policy of allowing four-plexes and row houses will produce on its own. So we're not really trying to argue with the numbers or the need, but rather to make observations about process.

Let me propose three rules of thumb for helping Strong Towns advocates think about addressing the housing crisis at scale, but also in ways that are as antifragile as possible.

1. Don't pick winners and losers. Let productive places reveal themselves.

Many cities have a "trickle or fire hose" problem, where development is intensely concentrated in just a few hot areas. In the county I live in, more than half of all new construction in 2016 occurred in just three ZIP codes, out of 27 total. In the rapidly-growing Seattle metropolitan area, I've documented that most residents live in neighborhoods that are virtually unchanging, while a small minority of areas undergo dramatic change (such as the Central District, which has gone from 70% African-American to only 20% in the face of rising rents and displacement).

This problem is exacerbated by public policy in two ways. One, many neighborhoods are virtually prohibited by their zoning from developing enough new homes to actually meet demand. Allowing the development of triplexes and ADUs is one way to loosen that straightjacket, but Cortright is almost certainly correct that there are places where it isn't enough to stabilize prices and let the neighborhood grow at the rate that it organically would in the absence of regulation.