The IG Metall union secured a 3.4 percent pay increase for its workers this year, and the country’s first minimum wage, €8.50, took effect in January. But wage growth in the service sector has not kept up.

Last month, members of the union of locomotive engineers, known by its German initials G.D.L., walked off the job for 138 hours — the longest rail stoppage in Germany’s history and the ninth rail strike in 10 months — as they sought a 5 percent wage increase. Talks between union representatives and the main German rail operator, Deutsche Bahn, began again last week and are expected to last until June 17.

Pilots for Lufthansa and its subsidiaries have held 12 rounds of strikes since April 2014 that came to an abrupt halt after the crash of a Germanwings flight over southern France in late March. The two sides agreed in mid-May to return to negotiations, and the pilots said they would keep flying until at least the end of July.

Postal workers are preparing to walk off their jobs indefinitely starting on Monday, in an effort to seek more pay and job security, while employees at Amazon’s main distribution center started a 48-hour strike early Friday, pressing the Internet giant to enter into a wage agreement.

In the case of the child care workers, the dispute follows five years in which Germany increased its emphasis on early childhood education, investing €12 billion to expand public facilities with a goal to create a guaranteed place for every child younger than 3. The program was part of an effort to better integrate immigrant children and to help women remain in the work force after starting families.

At the same time, caregivers were given more educational responsibilities, such as assessing children’s verbal skills and school readiness, which required extra hours of training. Verdi, which has two million members, argues that the government failed to adjust wages to reflect the heightened expectations.