The concept of securitization is generally associated with the Copenhagen school of security studies, which is generally taken to include Ole WÃ¦ver, Barry Buzan, and a range of other, more loosely associated, researchers.
Average annual number of employed coal miners in the United States, 1890-2014. US employment in coal mining peaked in 1923, when there were 863,000 coal miners. Since then, mechanization has greatly improved productivity in coal mining, so that employment has declined at the same time coal production increased. The average number of coal mining employees declined to 65,400 in 2015.
Coal mining employed 4,000 workers at 30 locations in 2013, extracting 13 million tonnes of coal. The three deep-pit mines were Hatfield and Kellingley Collieries in Yorkshire and Thoresby in Nottinghamshire. There were 26 opencast sites in 2014, mainly in Scotland.