German industry saw 2.002 million strike days in 2015, five times as many as in the year before and the highest level in 10 years, according to data compiled by the WSI economic think-tank.
The number is the combined total of all the working days on which employees staged walkouts or downed tools.
"2015 was an unusually intensive strike year," said WSI, an affiliate of the Hans-Böckler Foundation which has close ties to Germany's labour unions.
The substantial increase compared to 2014 - when there were just 392,000 strike days - was largely attributable to two major industrial disputes: one by pre-school kindergarten educators and another at the former postal monopoly Deutche Post, the foundation said.
Those two disputes accounted for 1.5 million strike days alone.
The number of employees who striked stood at 1.1 million, up from 345,000 in 2014, the statement continued.
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People tended to remember those strikes because they directly affected the public at large, the foundation said.
At the same time, multiple walkouts were staged in the metalworking sector in the context of the annual wage negotiations at the start of last year, but they tended not to stick in people's memory because they did not infringe on day-to-day lives of the population as a whole.
WSI said it was "unlikely" that a similarly high number of strike days would be seen this year, with no major industrial dispute currently on the horzion.
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On an international comparison, strikes in Germany are still relatively few, WSI said.
The annual average of strike days for every 1,000 employees stood at 15 in Germany between 2005 and 2014, a long way behind 132 in France, 124 in Denmark and 63 in Spain, it calculated.
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