With all the filthy lucre sloshing around on Wall Street, New York City may not strike you as a bastion of organized labor. But the city is in fact the nation’s leading union town. And in the past year, according to researchers at the City University of New York, there has even been a slight increase in unionization in the five boroughs.

About 24 percent of wage and salary workers in New York City are union members, a small but significant increase over the past year, from about 21.5 percent in 2012 . Statewide, according to Current Population Survey data analyzed in the study, New York remains the most union dense state in the country at 24.6 percent of workers.

According to the authors, Ruth Milkman and Stephanie Luce, the increase—amid a multi-year trend of decline—appears to be driven by hiring trends, not organizing new sectors. As the so-called “recovery” boosts labor demand, long unionized industries are just hiring more. “There are some new organizing efforts here and there, but nothing that accounts for this [increase],” Milkman tells The Nation. “It seems to just be shifts in the labor market reflecting long-unionized sectors that are rebounding.”

Union density in a large population offers only a rough gauge of actual labor activity. The overall number of union members may fluctuate from year to year whenever big unionized industries add or shed jobs, Milkman explains, but that does not capture, and could even mask, the effect of new union formation in smaller-scale workplaces—like the handful of immigrant workers who have recently unionized at local carwashes.

Much of last year’s growth in union workers has come in the construction industry, where unionization in the NYC metro area is about 27 percent, and 30 percent statewide—about twice the industry rate nationwide. But construction trades are a mixed bag, because employers can use both union and non-union workers on different jobs, and the industry runs on short-term contract work. Milkman says the recent trendlines point to growth in both union and non-union construction jobs, but with relatively strong growth among union members.

Overall, New York’s unionization rates are highest in the public sector, at about 70 percent. But surprisingly, recent expansion of union membership centers on private-sector workplaces. Alongside union boosts in the building trades, unions have made gains in building-based services, like janitors and porters, and hotels, where over a third of the labor force is union.

Though undocumented immigrants often work non-union jobs, immigrants (who make up about 37 percent of the city’s population) are rapidly joining the union ranks. Though newer immigrants have relatively low rates of unionization, according to the report, among immigrants who arrived before 1980, the rate is actually higher than that for US-born workers in both New York City and statewide. Black unionization rates have been the highest of any racial or ethnic group, Asians the lowest.

Though union workplaces generally offer higher wages and better benefits, union jobs face multiple threats from displacement and eroding working conditions. Building trades employers, for example, have recently shifted away from a longstanding agreement to stick to using union labor, enabling large developers to hire cheaper non-union and “off the books” workers, including many undocumented immigrants. A “two tier” labor structure, in which union and informal workers “compete,” may squeeze down job quality and undermine wages across the sector, by constraining workers’ ability to negotiate working conditions. A new condominium development plan in mid-town Manhattan seems to exhibit how the city’s economic “recovery” is banking on this trend. According to Crains, the project was recently sealed with “a special package of work-rule and wage concessions from construction unions that is expected to shave as much as 20 percent off labor costs—a savings of millions of dollars.”

According to a 2007 report by the think tank Fiscal Policy Institute, the prevalence of “underground” non-union construction workers led to hundreds of millions of dollars in hidden social costs, due to unpaid payroll taxes and public healthcare spending.

The city’s relatively high union density is rooted in a historical legacy of labor militancy, particularly in blue-collar trades and public services like mass transit. Over the course of the twentieth century, tough union shops cultivated what Milkman calls a workplace culture of “social democracy.”

Yet unions have not significantly penetrated newer, rapidly growing, service industries like retail and restaurants. Meanwhile, New York’s established manufacturing sectors maintain relatively high unionization rates, but the city has shed about half its manufacturing jobs since 2001.

Nonetheless, unions are more welcome in New York than most places in the country. Nationwide, unionization has tumbled since the 1980s after decades of deindustrialization and global offshoring. Today, only about 11 percent of workers belong to a union, and the right-wing backlash continues with “right to work” legislation, which impedes union organizing, and attacks on public sector collective bargaining rights.

Andrew Friedman of the Center for Popular Democracy, which advocates for low-income workers and communities of color, says “the vast majority of New York’s workers are not unionized, do not have a voice at work and are forced to confront ever-more exploitative treatment at work.” For the city’s working class as a whole, Friedman says via e-mail:

Not withstanding this recent uptick in unionization rates, far too many workers, particularly workers of color, women and immigrant workers, in particular, continue to receive inadequate wages, inadequate hours, inadequate control over their schedules and inadequate respect and dignity on the job.

Unions are not the only way to empower workers. Recent efforts to “organize the unorganized”—the unprecedented wildcat mobilization of non-union fast-food workers, organizing day laborers through worker centers, or community-driven campaigns for a $15 minimum wage—all illustrate the promise as well as the challenges of building labor power, with or without a formal union.

The right to good, safe jobs is universal; unionization is sadly not. But the struggle is the same whether you’re a hotel housekeeper striking for a better contract, or a day laborer suing for unpaid back wages. New Yorkers are holding onto traditionally unionized jobs. But a revival of the labor movement requires building new traditions of organizing in workplaces where activism makes the most difference.