By Kris Maher and Eric Morath 

The strengthening economy and tight labor market are giving workers more confidence to demand employer concessions through strikes.

In recent weeks, unionized hotel housekeepers in Chicago, distillery workers in Kentucky and crane operators in Seattle have all walked off the job to pressure employers for better pay and benefits.

Some 31,000 teachers in Los Angeles are threatening to strike, and union members at ArcelorMittal SA and U.S. Steel Corp. have given the authority to strike if negotiations break down.

With the national unemployment rate at 3.9% in August, just above an 18-year low, and skilled workers in scarce supply, union officials say they have more leverage at the bargaining table and that workers are more comfortable with the risks associated with striking.

Labor disputes have caused workers, excluding teachers, to miss 633,000 days on the job this year through August, up from 440,000 in all of last year, according to the Labor Department. Including the wave of teacher strikes in the spring, there were more than 2 million days missed, the highest level since 2006.

"They see the economy is growing, but their share of it is not," said Thomas A. Kochan, a professor of industrial relations at MIT's Sloan School of Management. The economy has shifted the bargaining power toward labor. "We have not seen that take place in years."

Strikes and other labor-related work stoppages had declined for decades, as the share of workers belonging to unions fell. The number of major strikes involving more than 1,000 workers has dropped in recent decades. Labor disputes, which tend to rise during good economic times and fall during recessions, reached a record low in 2009.

Public-sector unions suffered a blow in June when the Supreme Court ruled that government employees can't be compelled to pay union fees, which has cut into the coffers of the politically powerful unions.

"Now is the time to make sure we're delivering," said Christian Sweeney, deputy organizing director at the AFL-CIO. "If you're not going to do it when there's 4% unemployment, when is it going to happen?"

Wages have been growing at a fairly modest pace relative to the historically low unemployment rate. Nonsupervisory, private-sector workers' average hourly earnings rose 2.8% in August from a year earlier, the Labor Department said. While that matches the best annual gain since 2009, it is well below the 4% rate of wage growth recorded in late 2000, when unemployment was last similarly low.

Wage increases for factory workers have been slower than average. Hourly earnings for nonsupervisory workers in metal manufacturing, which includes steel mills, rose 1.1% in August from a year earlier.

A statewide teachers' strike in West Virginia that started in February resulted in a 5% pay increase for teachers and changes to the state public employees' insurance program, as well as increases for other state employees, more than state officials had previously offered.

Teachers who walked out over the next several months in Oklahoma, Kentucky, Arizona, Colorado and North Carolina won some pay increases and pension plan changes but not as much as unions had sought in many cases.

Earlier this month, the union representing crane operators in the Seattle area ended a 17-day strike after reaching a tentative agreement with a 17.8% increase in pay and benefits over three years. The union had rejected a 15% increase before it went on strike.

"In an era of general prosperity, when companies are generating greater profits, unions see the need to share that and are more willing to take direct action to get it," said Gary Chaison, a professor emeritus of industrial relations at Clark University.

In Chicago, roughly 5,000 housekeepers and other workers at 26 hotels went on strike on Sept. 7, demanding increased health-care coverage for newer employees, among other things. Unite Here Local 1 has argued that hotels are making record profits and should grant better benefits.

"It was a good time to go on strike," said Tina Graham, a 60-year-old housekeeper who has worked at the Palmer House, a Hilton Worldwide Holdings Inc. property, for 11 years and now earns $19.75 an hour.

She said the union wants year-round health-care coverage for workers typically laid off in the winter before being called back in the spring. The union also wants to cut the number of rooms workers like Ms. Graham need to clean per shift to 14 from 16 currently.

A Hilton spokeswoman said the company is committed to negotiating in good faith and values its employees.

Michael D'Angelo, vice president of labor relations at Hyatt Hotels Corp., said his company, also a target of the Chicago strike, was disappointed that Unite Here chose to walk out when negotiations are ongoing. Mr. D'Angelo said the company offers workers competitive wages and good benefits, including health care and retirement contributions.

"Hyatt has a long history of strong labor relations," he said.

A Marriott International Inc. spokesman said the company reached a contract agreement with the union on Thursday, but declined to provide specifics. The union said the agreement covers 1,200 workers.

In Michigan, highway construction projects across the state are stalled because the Michigan Infrastructure & Transportation Association, which represents contractors, has locked out heavy-equipment operators.

Mike Nystrom, a spokesman for the contractors association, said the operating engineers' union has turned down a 14.4% increase in total compensation. "They self-authored a contract and have put in it everything they've ever hoped for and wanted," Mr. Nystrom said.

Dan McKernan, a spokesman for Local 324 of the International Union of Operating Engineers, which represents more than 1,000 affected heavy-equipment operators, said the union wants individual contractors to agree not to hire nonunion subcontractors. He said the tight labor market has strengthened the union's hand.

"In a different economy, these contractors would have gone right out to get people to fill these positions," Mr. McKernan said. "They just don't have that ability right now."

Officials with the United Steelworkers say steel giants ArcelorMittal and U.S. Steel are asking for concessions rather than sharing profits, which have been helped by tariffs on foreign metals.

Contracts for both companies expired Sept. 1. Both companies are asking workers to pay more for health care.

U.S. Steel said its offer contains significant wage increases and choice between quality benefits plans and that the two sides are continuing to work toward "a mutually agreeable conclusion."

ArcelorMittal reported health-care costs per employee are up 78% since 2008, and the company said it is working to reach an agreement with the union.

In Lawrenceburg, Ky., 53 workers at a Four Roses bourbon distillery and bottling plant have been on strike since Sept. 7. Jeffrey Royalty, a distillery worker and president of United Food and Commercial Workers Local 10D, said the sticking point is proposed changes to paid sick-day plans for new hires.

"A claim that we are proposing a 'two-tier' sick leave policy that discriminates against new hires is not true," the company said.

The union says the plan for new hires is inferior and is in fact a "two-tier" proposal. "I'm just a country gentleman, but I don't need a dictionary to tell me that," said Mr. Royalty.

Write to Kris Maher at kris.maher@wsj.com and Eric Morath at eric.morath@wsj.com

(END) Dow Jones Newswires

September 23, 2018 07:14 ET (11:14 GMT)