Danish law does not require fast-food companies or their franchisees to adhere to the wages required by the agreement with the 3F union. But they do, because employees and unions pledge in exchange not to engage in strikes, demonstrations or boycotts. “What employers get is peace,” said Peter Lykke Nielsen, the 3F union’s chief negotiator with McDonald’s.

McDonald’s learned this the hard way. When it came to Denmark in the 1980s, it refused to join the employers association or adopt any collectively bargained agreements. Only after nearly a year of raucous, union-led protests did McDonald’s relent.

In interviews, Danish employees of McDonald’s, Burger King and Starbucks said that even though Denmark had one of the world’s highest costs of living — about 30 percent higher than in the United States — their $20 wage made life affordable.

True, a Big Mac here costs more — $5.60, compared with $4.80 in the United States. But that is a price Danes are willing to pay. “We Danes accept that a burger is expensive, but we also know that working conditions and wages are decent when we eat that burger,” said Soren Kaj Andersen, a University of Copenhagen professor who specializes in labor issues.

Measured in Big Macs, McDonald’s workers in Denmark earn the equivalent of 3.4 Big Macs an hour, while their American counterparts earn 1.8, according to a study by Orley C. Ashenfelter, a Princeton economics professor, and Stepan Jurajda, an economics professor at Charles University in Prague.

And the Danish restaurants are less profitable. With fast-food wages in the United States so much lower than in Denmark, and the price of Big Macs in the two countries similar, Mr. Ashenfelter said, “It must be that U.S. McDonald’s are far more profitable.” The higher wages and the higher menu prices help explain why there are 16 McDonald’s per million inhabitants in Denmark, but 45 McDonald’s per million in the United States, Mr. Jurajda said.

McDonald’s declined requests for detailed financial data for its restaurants. But it said in a statement that the countries where it operates “have significantly different cost structures, economic environments and competitive frameworks.” The company added that it and its franchise operators “support paying valued employees fair wages aligned with a competitive marketplace.”