“It’s too divisive,” she says, about Yes in My Backyard, a growing pro-development movement. As part of the leadership team of Engine 6, an affordable-housing group based in Newton, Massachusetts, Weissberg was instrumental in assembling a broad coalition to get two Newtonville housing developments approved over the vociferous objections of NIMBY—Not in My Backyard—advocates. Both developments—28 Austin Street, a 68-unit development, and the 140-unit Washington Place complex—have 25 percent affordable housing components, 10 percent higher than required by Newton law.

“The people on the other side were NIMBYs and were very loud,” she says. “They accuse us of being in the pocket of developers. But we’re not. We are in favor of development because Newton needs more diverse and affordable housing units.”

Dating back decades, NIMBYism’s supporters object to new development in general, especially near their homes. Adherents of YIMBYism see themselves as the opposite of obstructionists who hold that more building—especially housing—is a good thing and that the new supply will not only help middle-class tenants and buyers but also trickle down to the homeless and others at the margins of society.

The clash has become highly contentious in urban housing circles. NIMBYs are branded parochial and selfish; YIMBYs are accused of being naive about urban economics and stooges for the real estate industry. It is all the more controversial in areas with chronic housing shortages, Boston and San Francisco being two prominent examples.

It has also become a subject of academic inquiry. A 2017 study by Boston University, relying on minutes of local government meetings, found that the average NIMBY pretty much fits the stereotype: an older white male, a homeowner, a longtime resident, and a voter in local elections. A fresh-off-the-press 2019 study by Massachusetts Institute of Technology (MIT) suggests that the YIMBY narrative of more supply benefiting everyone is flawed, saying that higher housing density leads to higher prices, not affordability.

Civic officials in Massachusetts find themselves right in the thick of the NIMBY/YIMBY controversy. Andrea Kelley, Newton city councilor at-large, falls decidedly in the YIMBY camp and was a vocal proponent of both 28 Austin and Washington Place.

“The more that is built, the more opportunities there are,” she says, adding that NIMBY groups such as Newton Villages Alliance are populated by relatively few but very active people.

“Is the loudest voice the one you always listen to?” she asks. As an at-large councilor, she adds, she is free to consider the greater good for the overall city and represent underserved groups. “My job is to stand up for the single mother who doesn’t have time to come to City Hall. I believe we have a responsibility to be part of filling the regional need for housing.”

Then there’s the thorny aspect of class distinctions and racial stereotypes. Robert Friant is managing director of External Affairs for the New York City–based Corporation for Supportive Housing. “YIMBY is about the unlimited possibilities affordable housing brings to a city,” and, by contrast, “NIMBY is sometimes based on the uglier side of the table, contending that housing with an affordable component increases crime and decreases home values. We have studies that prove neither is true.”

What are the political and demographic forces at work in the ascendance of YIMBY? According to Clayton Nall, assistant professor of political science at Stanford University, the key distinction between NIMBY and YIMBY is that the latter is replete with high-earning young professionals.

“In the Bay Area, it’s possible for a young person to earn what nationally would be considered a high salary and still not be able to afford a home, to rent or to buy,” he says. “If you talk to the YIMBYs, they’re responding to the supply side, saying basically, ‘We just need to build more housing.’”

Nall describes the problem on the West Coast as extreme, with property values so high that “people with good jobs (are) joining the ranks of the homeless.” It has led to previously unimaginable efforts by California politicians to wrest control of zoning from local jurisdictions. Senate Bill 50, dubbed by supporters as the More HOMES (Housing, Opportunity, Mobility, Equity, and Stability) Act, would have allowed the state to impose zoning changes, clearing the way for substantially more dense housing, especially at existing transit hubs. It was endorsed by an organization called California YIMBY but was recently blocked by California lawmakers.

“NIMBYism is looking old to a lot of Millennials and Generation Xers,” says Miriam Axel-Lute, an Albany, New York–based editor of Shelterforce magazine, a housing advocacy publication begun in 1975. “The new groups don’t have skepticism about developers. YIMBYism appeals to the libertarian streak that a lot of them have. It’s Econ 101.”

Axel-Lute herself is skeptical. “No matter how much market-rate housing is built, it’s not going to trickle down to the ones who really need it.” But the new voices have value because “YIMBYs acknowledge that we need more public support for affordable housing.”

As if to affirm her contention, Yonah Freemark, a doctoral candidate at MIT who conducted the 2019 study, found that up-zoning (basically allowing for more and denser development) in Chicago between 2013 and 2018 did not increase supply or make housing more affordable but instead upped property values—not exactly in the YIMBY playbook. “There was a 10 percent to 20 percent increase in property values,” Freemark says.

Closer to Boston, Jesse Kanson-Benanav, chair of the leadership committee of A Better Cambridge, a YIMBY group, frames the movement in terms of dense, healthy urban environments versus suburban sprawl. “We believe we are at a turning point,” he says. “People, especially young people, are making the decision to live in cities.”

The group cites the basic unfairness of Cambridge being so expensive and exclusive—indeed, the city’s population is now 110,000, versus 120,000 in 1950. It’s within a 30-minute transit commute of more than 250,000 jobs, in essence at the epicenter of Greater Boston’s economy. Its excellent transit infrastructure means it offers not just job opportunities but potentially less car dependence.

“Current zoning has limited who, like people of color, can live in communities,” Kanson-Benanav says. “White property owners are primarily concerned about new development eroding property values. But we have evidence that that is not the case. But it’s still part of the opposition. People buy into this false argument.”

In Roslindale, a residential neighborhood of Boston, YIMBY activist Alan Wright sees the movement and urbanity as mutually supportive. “The basics of NIMBY opposition comes down to traffic congestion,” he says. “But that’s old thinking. The younger generation is taking mass transit, Ubering, and don’t want the hassle of having two cars.”

Joel Bloom, a resident of Newtonville, is in favor of both the Austin Street and Washington Place developments. “We have a low amount of economic diversity in Newton,” he says. “As a native New Yorker, I don’t buy into the negative stereotypes about affordable housing. I could be a candidate myself for selling my house and moving into an apartment.”

He adds that a vibrant mix of retailers at Washington Place would improve the neighborhood. “We need a bookstore, a camera store, and a good New York pizza place.”