QUICK QUIZ: What share of developable land in the state’s 177 MBTA Communities does the new zoning “mandate” apply to? Given the pitched debate over things like Milton’s referendum vote not to comply, the answer might surprise you: 0.60 percent.

Next question: How many housing units does it require to be built? Zero.

If those answers don’t match what you’re hearing around the MBTA Communities law, you’re not alone. Its real impact will be far less than the rhetoric from both sides of the debate. Proponents tout it as a transformative effort to tackle racial segregation and build affordable housing in our region’s most exclusionary suburbs. There is truth in these claims. But now that we’re shifting to implementation, I worry that overstating the law’s magnitude has contributed to the blowback.

To borrow a baseball analogy, MBTA Communities is a clutch hit. But it’s more likely a single than the promised (or threatened) home run.

As written, the law only requires that communities develop 50-acre zones where multifamily housing development is allowed as a right. Even within these small zones, municipalities retain extensive local control to determine things like the shape and form of what is allowable. And the required density in these zones is usually quite modest. Think triple-deckers or, for a few communities, small apartment buildings, not high rises.

It’s telling that opponents have also emphasized the law’s bigness, knowing that inflating its scope helps galvanize the resistance. Opponents in Newton, for instance, distributed “Save Our Villages” lawn signs depicting downtown-Boston-scale high rises, far more housing than anything required by the law. And in requesting a waiver from the law, the Wrentham Select Board just wrote a letter to the governor claiming that it requires their town “to increase our population by as much as 13 percent,” also a wild exaggeration.

A key source of confusion has been the big topline number of 297,000 new units that need to be zoned for under the law. Proponents have emphasized this number with enthusiasm for the change it’s hoped to bring. Opponents use it to exaggerate the potential construction – and new residents – that would result.

So, what’s the likely reality? A precise estimate is impossible, but here’s some back-of-the-envelope math showing one scenario for how things might play out:

  • While many municipalities will do the bare minimum to comply (or refuse to comply at all), many others are choosing to do more, so I’ll start by being generous and bump the estimated increase in zoned capacity up to 400,000.
  • That’s not all new zoning, though. Municipalities can draw their zones around existing housing, with 400,000 representing gross zoned capacity, rather than net new zoned capacity. Several places that already have housing density near transit—like Cambridge and Salem—can comply almost entirely by using existing zoning around existing housing. Other communities will have to adopt new zoned capacity, but even here, most will draw their zones around some preexisting housing. Taking a very round number, I’ll estimate that 50 percent of the gross topline number is truly new zoned capacity, bringing the total down to 200,000.
  • And that number is just what is allowable under zoning. It’s not a construction requirement. The vast majority of property owners in these new zones will be happy to stick with what’s already built and won’t redevelop their land for new housing. I live two blocks from a Green Line stop in Somerville, and our city’s compliance plan will likely allow me to add another unit or two on my property. I love that new flexibility, but our home was renovated eight years ago, so we definitely won’t build anything anytime soon.

For a report that Boston Indicators conducted a few years ago with economist Jenny Schuetz, we looked at the actual redevelopment activity in metro areas with similar transit-oriented upzoning changes. We found that between 5 and 10 percent of properties tended to be redeveloped within 5 years of the upzoning being enacted. So, for this exercise, let’s go with the upper end 10 percent development rate. In five years, that would yield 20,000 new units (or 40,000 over 10 years).

20,000 units of new housing – that’s no small feat. But it’s not going to dig us out of our much larger housing production hole. Take, for instance, the Metropolitan Area Planning Council’s target of building 154,000 new units in Greater Boston by 2030. 20,000 units would only get us 13 percent of the way there.

Overstating things raises the temperature of the debate unnecessarily, playing into fears about big change coming too quickly.  People are more small “c” conservative than we appreciate, even in a place like Massachusetts. Far better would be to reassure friends and neighbors about what the law really is: a commonsense plan for adding a little more vitality and a little more housing near suburban transit. One can even argue that, rather than top-down mandate, it is a modest expansion of property rights, giving homeowners a bit more flexibility to do what they want with their land. An approach like this reflects the truth of the law. And it’s more strategic on the politics.

The risk isn’t just that the current law might get undercut by the rhetoric. Today’s overpromises may also complicate tomorrow’s reform efforts. What if despite all the lofty rhetoric about MBTA communities, we still have a housing shortage 5 or 10 years from now? Will people lean into more efforts, or see upzoning as a failed test?

We can learn from the state’s steady, multi-year efforts on criminal justice reform. A sequence of smaller, yet still meaningful reforms were passed starting with Gov. Deval Patrick in 2010. Momentum grew over several years, and across multiple pieces of legislation, and culminated in the landmark passage of a pair of comprehensive criminal justice reform laws in 2018. Today, Massachusetts has the lowest incarceration rates in the country paired with continued declines in violent crime.

A more housing-focused model is California’s recent steady stream of housing production legislation. After housing advocates narrowly failed to pass the very ambitious The More Homes Act (or Senate Bill 50) in early 2020, they shifted their scope, instead passing more than 100 commonsense housing reforms since 2017 designed to spur new housing production. And they’re seeing tens of thousands of new units finally getting built.

People might read me as critiquing the law. But no, far from it. MBTA Communities is a smart, incremental step towards building more housing in strategic locations across Greater Boston. And the implementation timeline, which prohibits indefinite stalling through endless local process, has forced swift action with the right level of urgency. I’ve been inspired watching town after town adopt some multifamily zoning over just a few short months.

And, to be clear, we should allow far more housing than this around transit nodes in Greater Boston—think, for instance, of the vibrant mixed-use housing and commercial neighborhoods surrounding commuter rail stations in a place like greater Toronto. It’s just that MBTA Communities simply doesn’t require anywhere near that level of housing density.

So, let’s save our political capital for the next round of housing legislation—either for a truly big swing on comprehensive housing reform, or for a series of modest follow-up hits. Presenting MBTA Communities as a commonsense leadoff would be a better strategy for success.

Luc Schuster is the executive director of Boston Indicators, the research center of the Boston Foundation.