Year | Value | 2022 | 17.772188403495 | 2021 | 20.885343301269 | 2020 | 24.250579740839 | 2019 | 21.77990161224 | 2018 | 19.593364311466 | 2017 | 10.314017448928 | 2016 | 20.076564714237 | 2015 | 27.201915969621 | 2014 | 28.540191288235 | 2013 | 25.983485007995 | 2012 | 21.335388184547 | 2011 | 17.13063767487 | 2010 | 24.107790350746 | 2009 | 34.245077496102 | 2008 | 47.642167052656 | 2007 | 47.022050322971 | 1981 | 38.0293653129 | 1980 | 49.559876832913 | 1979 | 32.664769586424 | 1978 | 38.610866365064 | 1977 | 25.223077409979 | 1976 | 12.616821120852 | 1975 | 10.612753370915 |
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