According to the European Environment Agency, the length of snow seasons in the northern hemisphere has decreased by five days each decade since the 1970s, thus increasing the demand for the production of artificial snow. Some ski resorts use artificial snow to extend their ski seasons and augment natural snowfall; however there are some resorts that rely almost entirely upon artificial snow production. Artificial snow was used extensively at the 2014 Winter Olympics in Sochi, and the 2018 Winter Olympics in Pyeongchang to supplement natural snowfall and provide the best possible conditions for competition.