New construction: Seattle needs more of this. Kelly O

"Meditate on this," San Francisco activist Sonja Trauss tells a crowd in a conference room overlooking Lake Union. "What's the difference between being able to afford something that's not available... and not being able to afford something that is available?"

The room sits in polite quiet.

"Nothing," Trauss says emphatically. "There's no difference. These are both ways that [housing] shortage manifests."

Trauss is preaching to the choir: a room of mostly white, mostly male Seattle developers working on plates of steak and green beans. You don't have to tell this group twice about the rules of supply and demand. But in another way, Trauss is screaming into the void.

All across Seattle, small fights are playing out over whether new buildings—new housing—should be built. These are fights about the scale and height of new buildings, neighborhood character, and whether Seattle is losing its "soul." They are tedious and they are hurting housing affordability in this city. But for the most part, the only people paying attention to these fights are the people who want to stop the growth. People like the developers in this room, who believe Seattle needs more growth to meet its massive influx of new residents, rarely show up to advocate for new housing unless it's their own project in question. The rest of the city's residents—who, if recent city council election results are any indication, favor new density over parochial NIMBYism—don't often show up, either.

Trauss, 34, is trying to change that in San Francisco and encouraging urbanists in Seattle to do the same. Trauss founded the San Francisco Bay Area Renters Federation, a blunt, tech-funded, grassroots organization that advocates for more housing in and around San Francisco and was recently profiled in the New York Times as an indication of that city's "cries to build, baby, build." The group is one of many across the country organizing under the banner of YIMBY ("yes in my backyard"). Next month, YIMBYs will convene in Boulder, Colorado, for a conference with discussion topics like "forging healthy alliances between housing advocates and housing developers" and "responding to anti-housing ballot measures."

"You guys actually have some non-industry pro-growth people," Trauss tells the Seattle developers. "Seattle has a lot of urbanists. It's just a matter of Laura actually starting a mailing list, and pretty soon you'll have your own pro-development citizen group."

In the crowd sits Laura Bernstein, a 40-year-old renter in the University District who recently quit grad school to spend this year studying urbanism on her own and figuring out how to expand the YIMBY movement in Seattle. Before becoming a middle-school teacher, Bernstein studied opera and plant biology. Now she spends her days having coffee with other urbanists, going to community meetings, and running the Twitter account @YIMBYsea.

At this time last year, Bernstein wouldn't be showing up in a story about YIMBYs. Then, she was working for a city council candidate who embodies the "not in my backyard" movement—Tony Provine. (By the end of his campaign, Provine was sending out mailers depicting bulldozers threatening to tear down single-family zones across the city. He lost in the primary with just 14 percent of the vote in his district.) Bernstein says when she started working for Provine, she thought he could serve as a bridge between pro-density urbanists and neighborhood advocates afraid of change. With enough reasoning, she thought, anybody could be convinced to welcome growth in their neighborhood.

"All of that idealism went right out the window the minute I started knocking on doors and talking to voters," Bernstein tells me over Skype while she's in Vancouver to see an interactive art exhibit about growth there. Knocking on doors is when Bernstein says she began "hearing how cynical of downtown, cynical of politicians, and so put upon [homeowners were], like 'They're doing this to us.'" By "this," the neighbors mean growth. It's a common refrain in Seattle's density debate that developers or city officials are inflicting growth onto neighborhoods. In fact, of course, new people will move to Seattle whether we build for them or not. The only thing we have control over—unless we decide to build a wall—is whether we're prepared for those new residents.

But Bernstein is holding on to some of her idealism. She doesn't like to use the term "NIMBY" and is deliberate about trying to meet with people she disagrees with. That sounds cheesy, but it makes her a rarity among the city's hardcore urbanists.

On social media, Seattle urbanists can be a condescending, dick-swinging crowd, dismissing the lived experiences of displaced and struggling renters because they're busy shouting about the faultless wisdom of the free market. ("NIMBYs are literally the worst," one tweeted as I was writing this story. "Economic terrorists.") The city's well-meaning pro-tenants movement, meanwhile, peddles tired caricatures of greedy developers and focuses almost exclusively on rent control as the solution to Seattle's housing crisis. It's an exhausting split that accomplishes little, except alienating everyone in the middle. A group like SFBARF, led by renters and fighting for growth, could bridge some of that divide. Trauss is wholly pro-development—all types of it—but she also supports increased protections to keep renters from being "economically evicted" (when landlords dramatically raise rents to push out low-income tenants) and temporary rent control while supply catches up with demand.

Some local density advocates are skeptical of the YIMBY movement.

"Look at the math," Ben Schiendelman, a Seattle tech worker and outspoken pro-density provocateur, says of Trauss's efforts in San Francisco. "They don't win fights, and when they do, it's like for a handful of units in a building. In the time it takes to win those fights, you lose thousands of people out of the city."

Schiendelman, 34, believes the only answer in Seattle and San Francisco alike is to get rid of zoning altogether. (Trauss's group is trying to sue the suburbs for restricting growth; Schiendelman supports that and says he's working on a similar lawsuit against Seattle.) Killing zoning would allow all sorts of building all over the city, he argues, creating a denser, more transit-rich city where poor and rich people live alongside each other. He has little patience for community organizing like Bernstein and others are doing.

"People are becoming NIMBYs at a faster rate than you could talk them out of it," Schiendelman says. "The rate at which you could possibly organize [pro-growth] people is slower than the rate at which the city becomes less affordable."

But a look at the public reaction to modest moves toward more density in Seattle shows what an unwinnable fight getting rid of zoning altogether could be.

Last year, Mayor Ed Murray's housing affordability committee—known as HALA—recommended upzones to make certain parts of the city denser, reductions of expensive parking quotas, and new requirements that developers include affordable units in new apartment buildings or pay fees to help pay for new affordable housing. The neighborhood backlash was immediate, particularly against the recommendation to allow duplexes, triplexes, and backyard cottages in some of the city's single-family zones—which make up 65 percent of land (including parks) in Seattle. Meanwhile, others opposed HALA for different reasons. Developer lobbyist Roger Valdez argued the affordability requirements would make housing more expensive. Jon Grant, the former head of the Tenants Union of Washington State and a member of the HALA committee, criticized the recommendations for not including rent control and not charging enough fees on developers. In the middle, a coalition of developers and housing advocates have joined to form a group called "Seattle for Everyone," which encourages lawmakers and the public to support the HALA recommendations.

In response to neighborhood backlash, Murray, joined by Council Members Tim Burgess and Mike O'Brien (who claims to be the council's environmental leader), backed away from the HALA recommendations. It will be up to activists like Bernstein to force that discussion back onto the table. With calls to abandon all zoning set as the extreme, allowing backyard cottages and duplexes becomes the moderate position in this debate.

Bernstein says she's focused on what happens after HALA is done. The YIMBY movement "is here," she says. "I think we're a super YIMBY city."

Back at the developer dinner, Trauss urges builders to show up at meetings and comment in favor of each other's projects and to do an industry survey of their salaries to try to make the point that they're not all getting rich. In San Francisco, she's looking ahead to May 10, when she's asking YIMBYs to all show up and vote in an election on the same day to show that they're a real constituency.

"At the end of the day, some people just hate growth and there's nothing you can do," she tells the room. "You're never going to convince that person, so that's fine. Don't waste your energy. You just have to say, 'See you at the ballot box.'"