
Cambridge, Massachusetts, requires that 20% of the new space in larger housing developments include affordable homes. This, as we have talked about many times before on this blog, is known as inclusionary zoning (IZ). According to the Pioneer Institute, there are more than 141 communities in the state that have some sort of IZ policy.
But now, what is happening is that the numbers don't work on new housing projects. In the 30 years since the ordinance was enacted, it is reported that it helped create 1,603 affordable homes. However, since 2017 — the year the city increased the affordable requirement to 20% — only 200 new affordable homes have been created. That's approximately 20-22 new affordable homes per year — not much.
These numbers also don't speak to the number of new housing projects that could have been built, but weren't feasible precisely because of the IZ policy. This is the greater risk, because even new "luxury" projects help to relieve housing pressures within a market.
It is for this reason, along with others, I'm sure, that a developer is now suing the City of Cambridge, arguing that inclusionary zoning is unconstitutional on the grounds that it infringes upon people's property rights. To quote the developer, "I [would] have to build at a loss. Eventually, you just throw your hands up and say it doesn't work."
If successful, this case could help to change how cities tax new housing and how they aim to create new affordable housing, though I should mention that there have already been prior rulings on this issue.
Customarily, the way municipalities try to offset the burden of inclusionary zoning is to allow additional density and/or waive certain development levies. However, to accomplish this, you ideally need a planning framework where it's perfectly clear what maximum density would have been permitted without IZ.

