U.S. workers are doing something we haven’t seen much of in the last three decades: striking. Roughly 25,000 workers have recently walked off their jobs and joined picket lines, earning October 2021 the nickname #striketober.

Are these strikes likely to spread? Our research on union activity over the past century has identified several major factors affecting union and strike dynamics. How today’s strikes develop will likely depend on these factors.

Here’s the background on strike waves and strike droughts

We collected archival data on labor relations by industry from 1900 to 2015, including information on union membership, strikes and the number of workers involved, union elections, major legislation and the strategies used by unions and employers. We then applied historical and comparative methods to analyze why unions have been strong in some industries and eras and not in others.

The United States has been in a strike drought since the mid-1980s, with well under a half-million workers striking each year, and sometimes fewer than 100,000 workers — despite rising inequality and economic insecurity. In comparison, strikes were comparatively common for much of the 20th century. As the figure below shows, from the 1940s to the 1980s, between one and four million workers went on strike most years.​​

In 2018 and 2019, more than 400,000 teachers went on strike in different actions across the country. Combined with that surge, #striketober, and what’s being called the Great Resignation, workers are signaling that they are once again willing to take action when they have grievances.

Strike waves happen, in part, because workers reevaluate what they might be able to change in their own workplaces; societal conditions are favorable; and people see other workers successfully striking. Although we have had difficulty finding data on win rates for recent years, we found that strike win rates and strike activity moved together between 1916 and 1936. When workers were winning, more workers went on strike.

Strike outcomes: labor supply, strategy, and politics

Employees tend to win strikes when employers have a hard time replacing striking workers. When that happens, businesses can no longer produce goods or services, creating financial or political crises for employers.

So what factors make it hard to replace workers?

First, a tight labor supply gives workers more power during strikes. For example, during the world wars, with legions of working-age men fighting abroad, workers had the upper hand. Highly trained (especially licensed) workers in industries that are critical to the economy — like flight attendants or health-care workers — are also well-positioned for action because their critical skills make them difficult to replace. Most recently, the pandemic has brought workers new leverage. As workers have refused to return to jobs with low pay and poor conditions, they’ve become more difficult to replace — and remaining workers are more powerful during strikes.

Second, unions can adopt strategies to make workers hard to replace. Early unionists built the American Federation of Labor (AFL) through their apprenticeship training programs. Since craft unions were central in training skilled labor, employers couldn’t easily find replacements during strikes. In the 1930s, the rival Congress of Industrial Organizations (CIO) adopted a different strategy. Industrial organization unionized entire workplaces rather than only workers within a single occupation, using inclusiveness and worker solidarity to make them difficult to replace. Their initial spark came from a new tactic: the sit-down strike. Here, strikers “sat down” at their work stations. For employers to replace them and resume production, they first had to battle to move out each seated worker — making the sit-down strike highly successful.

Employers, for their part, have experimented with making workers easier to replace. That’s included automating tasks, de-skilling (or breaking down tasks so they are easily done by anyone), moving worksites to states or countries without unions, developing new legal relationships with workers (like sub-contracting or part-time work), or reorganizing tasks to enable work to continue even with high worker turnover.

Third, laws and government actions can also make replacing workers either easier or harder. In the early 1900s, courts often issued injunctions to stop strikes, and employers routinely fired striking workers. But in 1935, New Deal legislation established workers’ right to strike. With courts and regulations on their side and the CIO on the move, workers struck often — and won union recognition, wages and conditions that over several decades ushered in a new middle class.

By the 1980s the political pendulum had swung back. President Ronald Reagan permanently replaced striking air traffic control workers in the 1981 PATCO strike, symbolically legitimizing the replacement of striking workers. Since then, state laws and courts have undone protections for unions and strengthened employers’ rights.

The future of #striketober

In this pandemic moment, workers are again more difficult to replace. With millions quitting their jobs in what’s being called “the Great Resignation” and others unable to work because of a lack of child care or other supports, many businesses can’t find staff. And supply chains have been disrupted in unprecedented ways due to shortages of truckers, shipping containers, and covid workplace closures. In some ways, the moment is ripe for strikes: Workers have power and frustrations, and can see strikes succeeding elsewhere — including beating back concessions, sometimes just with the threat of a strike.

However, although most Americans approve of unions, 90 percent of wage and salary workers are not unionized. To win strikes, workers need more union support, experienced leaders, and strike funds.

How the government reacts will also influence any potential strike wave. Although President Biden expressed support in March for a unionization vote at Amazon, he has mostly refrained from speaking about recent strikes. But two of his Cabinet members have expressed solidarity with workers. Secretary of Labor Marty Walsh even recently visited Kellogg workers on a picket line. Symbolic solidarity like this helps striking workers.

Laws and friendly appointments would be even more effective, from appointing pro-labor NLRB board members to passing legislation like the PRO Act. The government could also take other actions. For example, in the 1930s, the federal government threatened to rein in powerful anti-union monopolies like the A&P grocery chain. It also established the LaFollette Committee to expose employer abuses and illegal actions.

The pandemic exposed and intensified a host of worker grievances, including inadequate wages, demanding schedules, historically high CEO compensation, and the notorious two-tiered wage system. These strikes, combined with the “Great Resignation,” suggest that many working people want better options. If they succeed, they could redefine the next generation of work.

Jasmine Kerrissey is associate professor of sociology and labor studies at the University of Massachusetts, Amherst.

Judy Stepan-Norris is research professor of sociology at the University of California, Irvine.