The golden years of coal mining ended in the late 1950s, after which production gradually diminished due to competition from cheaper Polish and American coal and the discovery of natural gas in the province of Groningen. In the period 1965–1975 the coal mines were closed altogether. In the area around Heerlen-Kerkrade-Brunssum and Sittard-Geleen 60,000 people lost their jobs. A difficult period of economic re-adjustment started. The Dutch government tried to ease the pain by moving several governmental offices (ABP, CBS) to Heerlen but even today the city has not fully recovered from the loss of tens of thousands of jobs.