An Affordable-Housing Quota Is a Number on a Permit, Not a Pile of Houses

An inclusionary housing quota doesn't build anything by itself. It's a condition attached to new projects, a share of homes at capped prices or a fee instead, and what it produces depends on what gets built under it.

Picture the list of rules pinned to a building permit.

In some cities, somewhere on that list, is a line saying that a slice of the new homes must be cheaper than the rest. That line is what people usually mean by an affordable-housing quota. Its formal name is inclusionary zoning.

It's tempting to imagine the quota as a stock of houses waiting somewhere. It isn't. It's a number written into the conditions for building. No building, no houses from the quota.

Two dials

The basic idea is short. Developers putting up market-rate housing, priced at whatever buyers or renters will pay, are encouraged or required to set aside a percentage of it to sell or rent below market.

That gives the quota two settings. One is the share: what percentage of the new homes have to be the cheaper kind. The other is the cap: who those homes are for, and therefore how much they can cost. Policies commonly peg the cap to a percentage of area median income, the middle household income for the area, with half of households earning more and half less.

Turn up the share and more homes are capped. Turn down the income target and each capped home has to be cheaper. Either way, the developer collects less from the project, and that's where most of the interesting consequences start.

Or pay instead

Some policies let the developer skip building the cheaper homes on the spot and pay money instead. That's an in-lieu fee: a fee paid in place of the homes, usually into a local affordable housing trust fund rather than to any particular household.

How big should it be? One common method starts from the affordability gap: the difference between the market price of a home and what a low- or moderate-income household can afford. If a typical market-rate home sold for US$300,000 and the affordable price was US$200,000, the fee would be US$100,000.

In theory, the fee should roughly match what it would cost to provide the home on site. In practice, it's typically lower.

Other policies let developers put the capped homes in a different project altogether, known as off-site provision, because building them in the same block isn't always feasible. Each route has a trade-off. Fees give developers flexibility, especially on smaller jobs, but can mean fewer capped homes in the building itself and less mixed-income development, where households on different incomes live side by side. Critics see the fee as a loophole that lets developers avoid contributing homes on site.

A toll on new building only

Here's the limit that shapes everything else. The quota attaches to new projects. It says nothing at all about the homes already standing.

So it's less like a tax on all housing and more like a toll on a new road: it only counts the traffic that actually uses the road. That's why inclusionary programmes tend to produce relatively small numbers of affordable homes each year. They rely on new development, and only collect when it happens.

It also explains why the details of who pays, and how much, matter so much. Some cities charge smaller projects a lower fee, on the grounds that their economics may be more marginal and a lighter fee could help them go ahead.

Boston, by postcode

Boston shows how the fee can be set by geography. In 2015 the city adopted a map dividing it into three zones by average housing cost, with a different fee for rental projects in each: US$200,000 per affordable unit in the lowest-cost zones, US$300,000 in the middle and US$380,000 in the high-cost zones.

Run the numbers and a rental developer skipping one affordable unit in a high-cost zone pays US$180,000 more than one in a low-cost zone, getting on for twice as much. The stated logic is that building capped homes on site costs developers more in pricier areas, so a higher fee there keeps the two options roughly comparable.

Homeownership projects work differently. There the fee is the greater of the zone's base rental fee or half the gap between the average market-rate price and the price of an on-site affordable unit.

Mandatory, voluntary, and the density bonus

Capped homes bring in less money than market-rate ones. That's the point of them, and it's also where the side effects come from.

In one economic model, cutting a developer's revenue, by raising the share of affordable homes or lowering the affordable rents, delays development when the developer can't choose how many homes to build. The general rule in that model: when costs rise relative to benefits, the project waits.

The usual counterweight is a density bonus, one of the most common incentives. It lets developers build beyond the density ceiling, the most homes the rules normally allow on a site, so more market-rate sales can balance out the capped ones. In the Washington, D.C. area, such bonuses range from 10 to 25 per cent. A bonus is worth more where prices or rents are higher, and it isn't really free: extra homes bring extra infrastructure and other public costs. Nor is a developer obliged to use all of it, if they'd rather build less.

That bonus is also the hinge between the two broad kinds of policy. A mandatory policy applies the condition to every qualifying project. A voluntary one offers a trade: affordable homes in exchange for extra density, a change to the land-use plan, or public funding. Voluntary programmes in California produced significantly fewer homes than mandatory ones, partly because most offered only fairly modest density bonuses. The sweetener has to be worth taking.

Fixed number, moving pile

None of this settles whether quotas are good policy; that turns on local rules, prices and builders. What the machinery does show is where the outcome comes from.

A quota is a condition on future building: a share, a price cap tied to income, or a fee in place of both, triggered only when a project comes forward. How many homes it delivers depends on how many projects come forward, how big they are, where they go, and whether the developer builds the homes or pays the fee. The number on the permit stays put. The pile of houses is up to everyone else.

SOURCES

1. Urban Institute, "Determining In-Lieu Fees in Inclusionary Zoning Policies" (PDF). https://www.urban.org/sites/default/files/publication/102230/determining-in-lieu-fees-in-inclusionary-zoning-policies.pdf (accessed 24 Oct 2026, via web.archive.org)

2. Grounded Solutions Network, "Setting the In-Lieu Fee." https://inclusionaryhousing.org/designing-a-policy/off-site-development/in-lieu-fees/setting-the-in-lieu-fee/ (accessed 24 Oct 2026)

3. Rick Jacobus, Lincoln Institute of Land Policy (2015), "Inclusionary Housing: Creating and Maintaining Equitable Communities" (Policy Focus Report, PDF). https://www.lincolninst.edu/app/uploads/legacy-files/pubfiles/inclusionary-housing-full_0.pdf (accessed 24 Oct 2026)

4. HUD User, working paper awm_rep_0902 (PDF). https://www.huduser.gov/Publications/pdf/awm_rep_0902.pdf (accessed 24 Oct 2026)