Coal production played a key role in the UK economy in the 19th and 20th centuries. In the mid-1970s, 130 million tonnes of coal were produced annually, not falling below 100 million tonnes until the early 1980s. During the 1980s and 1990s the industry was scaled back considerably. In 2011, the UK produced 18.3 million tonnes of coal. In 2005 it had proven recoverable coal reserves of 171 million tons. The UK Coal Authority has stated there is a potential to produce between 7 billion tonnes and 16 billion tonnes of coal through underground coal gasification (UCG) or 'fracking', and that, based on current UK coal consumption, such reserves could last between 200 and 400 years. Environmental and social concerns have been raised over chemicals getting into the water table and minor earthquakes damaging homes.