As unions shrink, work stoppages — usually strikes — have dwindled in recent years, from 834 nationwide in 1990 to 145 last year. But when a work stoppage does occur, it’s twice as likely to be a lockout as it was a decade ago, according to data compiled for the Globe by Bloomberg Law, a provider of legal research and business intelligence.

When National Grid locked out 1,250 Massachusetts gas workers in the predawn hours of June 25, the state’s largest gas utility landed another blow in a power struggle between labor and management that is increasingly tipping in employers’ favor.


This shift suggests that strikes have become a much weaker tool for unions, while management continues to lock out workers as a way to call the shots at the bargaining table.

“In the increasing pro-business climate in America over the last 25 to 30 years, and with the shrinking membership in unions along with that, employers now believe that they have more leverage and they have the upper hand,” said Robert Forrant, a labor historian at the University of Massachusetts Lowell.

This is especially true in companies that, like National Grid, can continue delivering their product to consumers with little to no interruption using replacement workers. Unless people are in need of new gas service, which is being put off as crews focus on emergencies, they still have hot water and can operate their ovens and dryers.

“Hardly any customers of National Grid right now, unless they’re paying attention, know there’s a lockout,” Forrant said.

The National Grid lockout started when the contract expired and the two unions involved refused to agree to the company’s proposals to increase health care costs and reduce benefits for new hires, including replacing pensions with 401(k) plans — changes that have been made in many of its other unions, National Grid said, not to mention in the majority of businesses and industries nationwide.


The unions offered to continue working under the old agreement, but the company opted to lock them out instead; 600 contractors and 700 supervisors are out in the field doing the jobs.

The union workers lost their health care coverage along with their wages, although, unlike in a strike, they can file for unemployment, which pays workers about half their annual weekly base salary, capped at $769 a week.

The locked-out workers make $120,000 a year, on average, including overtime, according to National Grid, although union leaders note that overtime is often required, and they have requested more workers to allow their members to work less.

The locked-out workers serve 700,000 gas customers in 85 communities in the state.

The UK-based utility recently reported a 24 percent annual increase in profits, and, like other companies, has benefited from the Trump administration’s corporate tax break.

President Marcy Reed has said the company is concerned about affordability, which is why it needs to control labor costs.

But the lockout is not just a way to force concessions from these two unions, said Forrant, the UMass Lowell labor historian. It is also a signal to other unions that they could face the same treatment.

“It has a chilling effect on contract negotiations,” he said.

It could also encourage other public utilities to flex their muscles, he noted.


Lockouts occur most commonly in the manufacturing and health care sectors, according to Bloomberg Law, although the highly publicized lockouts of professional sports teams are the ones most people remember. In 2011, the National Football League shut down operations for 18 weeks, and the National Basketball Association idled players for more than five months, delaying the start of the season.

Even the New York City Opera locked out its singers and orchestra for more than a week in 2012.

The rate of lockouts has been rising steadily through the decades, accounting for 4.1 percent of work stoppages in the 1990s, 5.4 percent from 2000 to 2009, and 7.8 percent since 2010.

For several years following the recession, as the effects of the economic downturn lingered and union workers faced stagnating wages and layoffs, the rate of lockouts jumped.

The National Grid lockout is the largest in the country since 1,200 nurses at Tufts Medical Center were locked out for four days after a one-day strike last summer. The National Grid lockout is the fourth against United Steel Workers since 2010 that has affected 1,000-plus workers; no other union has had as many lockouts of that size during this time.

A 2015 lockout of 2,200 union steelworkers at Pittsburgh-based Allegheny Technologies Inc., including 100 workers in New Bedford, was settled after more than six months following a National Labor Relations Board ruling that the lockout was illegal.

Lockouts are legal as long as employers are engaged in good-faith bargaining with a union. But the two steelworkers unions involved in the two-month-long lockout say this is not the case. They have filed numerous complaints with the NLRB, including claims that the company refused to provide relevant information about contractor costs, would not bargain over proposed changes to the safety handbook, declared an impasse prematurely, and tried to force the unions to bargain over an issue they are not required to negotiate.


If the NLRB declares the lockout illegal, National Grid could potentially have to reinstate union workers with full back pay.

National Grid said it “continues to bargain with these two locals in good faith and adheres to the rules of collective bargaining.”

The potential ramifications mean that companies are usually very careful to ensure their actions are legal before they undertake such a drastic measure, said Peter Stergios, a New York labor lawyer who represents employers. “It’s sort of like declaring nuclear war in labor relations,” he said.

John Buonopane, president of United Steel Workers Local 12012, which represents a third of the locked-out workers, said the unions have sent Governor Charlie Baker three letters about safety violations by replacement workers that the unions have reported to the Massachusetts Department of Public Utilities, which regulates National Grid.

The DPU responded to one of the letters, and a spokesman for the governor said that Baker encourages both sides to reach a compromise quickly, so that people can go back to work.

“He’s not getting involved the way he should,” Buonopane said of Baker, noting that the lockout could cost National Grid millions, including hotel rooms for out-of-state contractors, extra crew members manning gas leaks, and increased police details.


“It’s going to get passed on to the rate payer,” he said.

National Grid said it is “not planning to pass on to our customers any unreasonable incremental operating costs associated with our continuation workforce.”

The next negotiating session is scheduled for Friday.

Paul Baszkiewicz, 61, a crew leader at the “rainbow tank” in Dorchester, where liquid natural gas is vaporized, had been at Boston Gas Co., which was later acquired by National Grid, for only a few years when it locked out workers in 1993. Back then, the company paid for health insurance quarterly, he said, which meant that workers had insurance for three of the five months they were locked out.

Still, it was a stressful time, leading to drinking and divorces, he said.

“I fear for the younger people,” he said. “It affects your whole family.”

Katie Johnston can be reached at katie.johnston@globe.com. Follow her on Twitter @ktkjohnston.