mainly built around open end spinning techniques using rotors or ring spinning techniques using spindles. In 2009 there were 202,979,000 ring spinning spindles installed worldwide, with 82% of these being in Asia or Oceania and 44% being within China. In the same year there were 7,975,000 open end spinning rotors installed, with 44% of these being within Asia or Oceania and 29% within Eastern Europe. The average age of installed rotors is much lower than that of spindles and as rotors are between 7 and 10 times more productive they are responsible for 20% of the cotton spun worldwide. Modern cotton mills are increasingly automated. One large mill in Virginia in the United States employs 140 workers in 2013 to produce an output that would have required more than 2,000 workers in 1980. Locations Cotton mills were not confined to Lancashire but were built in northeast Cheshire, Derbyshire, Nottingham, the West Riding of Yorkshire, Bristol, Durham and the west of Scotland. The availability of streams or rivers to provide power determined the location of the early mills some of which were in isolated areas. In Lancashire they were built on the rivers and streams descending from the Pennines and Rossendale moorland. In some places quite small streams powered a string of small mills such as in the Cheesden Valley between Ramsbottom and Heywood. where 14 mills and their associated leats and ponds were concentrated along a four-mile stretch of the brook. Mills were built around Rochdale and Littleborough. North of Bury, ten mills occupied a mile long stretch of a stream in the Shuttleworth Valley. Other mills were built north of the River Ribble and a cluster of five mills in Caton near the port at Lancaster, one of which belonged to Samuel Greg who built Quarry Bank Mill at Styal in Cheshire. Not all water-powered mills were in rural areas, after 1780 mills were built in Blackburn and Burnley. In Scotland, four cotton mills were built in Rothsay on the Isle of Bute using labour that had experience of the linen industry. By 1800 there were two water-powered mills at Gatehouse of Fleet employing 200 children and 100 adults. Robert Owen who had worked for Peter Drinkwater in Manchester, developed the mills at New Lanark built by his father-in-law, David Dale under licence from Arkwright. Architecture Fireproof construction Cotton mills were huge fire risks, cotton fibres in the air