Parking Minimums: The Only Truly Effective Form of Inclusionary Zoning
Substitute "parking spot" for "housing unit" and these two policies are essentially the same.
I work in housing, and I am generally opposed to inclusionary zoning. IZ policies are usually complicated, add hassle and cost to projects, and rarely result in anything close to the number of "affordable" housing units needed for any market where they are implemented. I suppose people like them and still keep instituting them in some form (as Portland just did in their recent low density reform), because IZ feels like a penalty for eViL DEVeloPErs. As I see it, they're a sort of last ditch effort for obstructionists who hate any sort of multi-unit housing, and they allow for a final "gotcha" after the NIMBYs realize they can't block everything they want. I have also never really understood them because:
Most places that have inclusionary zoning policies also seem to have plenty of exclusionary zoning in the exact same code--why wouldn't you just subtract from those rules to make all building less complicated, rather than adding more regulations elsewhere?
At what point did everyone agree that it is a private developer's responsibility to resolve low-income housing needs project by project, rather than having the entire community take responsibility all together?
Do people not realize that the cost to build IZ/income-restricted units is usually exactly the same as the market units they share a wall with? Where do people imagine the price for that unit goes, other than bundled into the market units of the rest of the development?
I have never heard good explanations for any of these, at or any justifications that make a lot of sense. But I suppose I can understand that one reason these polices endure is because it makes it look like a municipality is doing something.
All that being said, there is one type of inclusionary zoning which has been remarkably successful in the US, and resulted in massive development of one very specific type of housing: minimum parking requirements, which have mandated huge amonts of housing for cars. After decades of minimum parking requirements in just about every municipality nationwide, at this point in the US there are about 8 parking spots for every car, a use of space which takes up about 30% of our cities. In contrast, according to the census, there only about 1.17 housing units for every household nationwide. That's 8-1 for car housing versus 1.17-1 for people housing. Clearly our building priorities of the last 50+ years have looked after some housing needs more than others.
And, even though the last few years have seen a lot more housing built, I doubt the housing to households ratio will improve too much any time soon--we've just built so little housing in the last 10 years that we likely have a lot of catching up to do:
Meanwhile during the same period I am sure cities have added thousands more parking spaces than the number of motor vehicles available (I don't have any data on this, but I don't think that car rates have increased that quickly over time).
So, as an inclusionary zoning policy that encourages the development of a certain type of space, parking minimums have worked great. Not only do drivers have multiple spaces to choose from wherever they go, in most cases they don't actually have to pay the cost up front for these spaces either. Contrast that with the pitiful housing inclusionary zoning policies, which over the years have produced only around 150,000 units nationwide, which people probably still have to pay for to use! It sounds crazy, but I'd wager that that's the number of parking spaces all of California builds in a couple of years.
I don't think inclusionary zoning is a great policy choice, but if any city is going to implement it they should do it like the other inclusionary zoning policies for cars: No complicated x% AMI requirements, no specific zones, just pure x units per x square feet or x units per whatever else based on land use. Want to build a new car dealership? 1 housing unit per 1000 square feet of car lot space. Want to build a new restaurant? 1 unit per 10 seats. Want to develop a new bowling alley? 1 housing unit per lane. Housing would get built everywhere, all the time, in every situation, in both urban and rural areas alike. What a situation to have so many housing units to choose from!
Sure, some of the units might not be terrific, but the point is there would be thousands more housing units built every year by fiat, and all households will have more options to choose from anywhere they wanted to live. At this point someone might argue that tying parking to land uses is different than tying housing to land uses, because parking mitigates a land use's impact--but this is complete nonsense. Land uses don't create traffic impacts, people do. Land uses outside of the ROW do not "generate" trips, or have anything to do with mode choice. Parking requirements are a public policy choice to make driving easy and avoid the responsibility of managing the street; inclusionary zoning requirements are a public policy choice to make low-income rental housing more plentiful and avoid the responsibility of building it publicly.
Of course, these minimum housing requirements would be expensive. In many markets in 2019, the cost to build (excluding land) a low-density single-unit house was often around $200,000-$250,000, an apartment $100,000-$150,000, and even the cheapest option of a manufactured home might be around $40,000-$50,000. This would increase total development costs, require more land, and ultimately end up in the price of goods and services. But parking minimums already do this to a lesser degree, and many people seem to be fine with it. And if housing people is something we care about, why wouldn't we require more of this too? Governments mandating that space be set aside for people housing is exactly the same type of regulation as governments mandating that space be set aside for vehicle housing, the difference is a just question of cost and size.
To conclude, I don't think inclusionary zoning is a very good policy choice, but if cities are going to do it then they should go all in and mandate a certain number of housing units with every single land use. If people don't like it, then it's time to have a larger discussion about values--and at the very least it reveals the absurdity of the minimum parking mandates that most cities already require.