U.S. workers continued to throw their weight around in a healthy economy in 2019, recording the largest number of major strikes in the decade.
The U.S. saw 25 work stoppages involving at least 1,000 workers last year, according to data released Tuesday by the Bureau of Labor Statistics. That was the most of any year between 2010 and 2019, a time span in which the average was 15.
The number of strikes is largely a reflection of the tight labor market, which has shifted leverage from employers to workers, coupled with the relatively slow growth in wages. Unions feel more emboldened to carry out strikes when many companies can afford to meet their demands and may have a difficult time finding replacement workers due to low unemployment.
The total number of workers who went on strike in those work stoppages was 425,500 ― fewer than the 485,000 in 2018, but still a hefty number by historical standards. Workers generally have not gone on strike in such large numbers since the mid-1980s.
According to the Economic Policy Institute, 2018 and 2019 accounted for the largest two-year average of striking workers in more than three decades.
Educators are still leading the way when it comes to walking off the job to improve their working conditions. They accounted for 13 of the 25 work stoppages last year ― including in Oregon, South Carolina, North Carolina, Kentucky, Colorado, Illinois and California ― and made up more than half of the workers who went on strike.
Last year’s teacher strikes were the continuation of a wave that began in West Virginia in 2018, as educators demanded more school funding, higher salaries and health care protections. What had begun as largely a red-state phenomenon eventually came to city school districts in Oakland, California, as well as in Denver, Chicago and Los Angeles.
Many of the strikes last year were massive, with 10 involving at least 20,000 workers. The largest in the private sector was the six-week strike at General Motors, in which 46,000 workers shut down production at dozens of facilities across the country before returning to work in late October.
The GM strike was the first prolonged work stoppage to hit the company in more than 20 years. The BLS data conveys just how much work was lost, with more than 1.3 million “days idle” ― the total number of workdays missed by all workers.
The next largest strike at a private employer took place at the New England grocer Stop & Shop. More than 31,000 workers in Connecticut, Massachusetts and Rhode Island were off the job for 11 days as they resisted higher health care costs and a two-tier system for new hires.
Although the number of strikes has been rising in the U.S., the share of workers belonging to a union has been hovering at a historic low. Only around 1 in 10 workers is now a union member, down from a high around 1 in 3 during the 1950s.
This article originally appeared on HuffPost.