Starbucks workers have added to the momentum of a union campaign that went public in late August and has upended decades of union-free labor at the company’s corporate-owned stores.
On Thursday and Friday, workers at six stores in upstate New York voted to unionize, according to the National Labor Relations Board, bringing the total number of company-owned stores where workers have backed a union to 16. The union, Workers United, was also leading by a wide margin at a store in Kansas whose votes were tallied Friday, but the number of challenged ballots leaves the outcome officially in doubt until their status can be resolved.
The union has lost only a single election so far, but it is formally challenging the outcome.
Since the union secured its first two victories in elections that concluded in December, workers at more than 175 other stores across at least 25 states have filed for union elections, out of roughly 9,000 corporate-owned stores in the United States. The labor board will count ballots in at least three more stores next week.
The organizing success at Starbucks appears to reflect a growing interest among workers in unionizing, including the efforts at Amazon, where workers last week voted to unionize a Staten Island warehouse by a significant margin.
On Wednesday, the general counsel of the labor board, Jennifer Abruzzo, announced that union election filings were up more than 50 percent during the previous six months versus the same period one year earlier. Ms. Abruzzo expressed concern that funding and staff shortages were making it difficult for the agency to keep up with the activity, saying in a statement that the board “needs a significant increase of funds to fully effectuate the mission of the agency.”
Starbucks has sought to persuade workers not to unionize by holding anti-union meetings with workers and conversations between managers and individual employees, but some employees say the meetings have only galvanized their support for organizing.
In some cases, Starbucks has also sent a number of senior officials to stores from out of town, a move the company says is intended to address operational issues like staffing and training but which some union supporters have said they find intimidating.
The union has accused Starbucks of seeking to cut back hours nationally as a way to encourage longtime employees to leave the company and replace them with workers who are more skeptical about unionizing. And the union argues that Starbucks has retaliated against workers for supporting the union by disciplining or firing them. Last month, the labor board issued a formal complaint against Starbucks for retaliating against two Arizona employees, a step it takes after finding merit in accusations against employers or unions.
The company has denied that it has cut hours to prompt employees to leave, saying it schedules workers in response to customer demand, and it has rejected accusations of anti-union activity.
As the union campaign accelerated in March, the company announced that Kevin Johnson, who had served as chief executive since 2017, would be replaced on an interim basis by Howard Schultz, who had led the company twice before and remained one of its largest investors.
Some investors who had warned Mr. Johnson that the company’s anti-union tactics could damage its reputation expressed optimism that the leadership change might bring about a shift in Starbucks’s posture toward the union. But the company soon announced that it would not agree to stay neutral in union elections, as the union has requested, dampening those hopes.
On Monday, the same day that Mr. Schultz returned as chief executive, the company fired Laila Dalton, one of the two Arizona workers the N.L.R.B. had accused Starbucks of retaliating against in March. The company said that Ms. Dalton had violated company rules by recording co-workers’ conversations without their permission.
“A partner’s interest in a union does not exempt them from the standards we have always held,” Reggie Borges, a company spokesman, said in a statement, using the company’s term for an employee.
