Year | Value | 2020 | 30.578986076458 | 2019 | 32.211262557282 | 2018 | 32.480170129145 | 2017 | 31.95625505647 | 2016 | 30.992308955907 | 2015 | 29.30214616524 | 2014 | 29.115927524125 | 2013 | 28.133301366711 | 2012 | 29.557528717975 | 2011 | 31.68650838695 | 2010 | 27.511642305244 | 2009 | 25.13288436263 | 2008 | 22.084701660805 | 2007 | 22.307209585779 | 2006 | 23.207912427058 | 2005 | 25.658598902702 | 2000 | 24.512781383683 | 1999 | 25.581613182345 | 1998 | 24.846665131574 | 1997 | 25.343676697858 | 1996 | 25.318209672143 | 1995 | 25.973655769136 | 1994 | 30.045124628224 | 1993 | 33.233977150579 | 1989 | 34.574951448071 | 1988 | 33.830335652672 | 1987 | 32.763381557632 | 1986 | 30.037056209796 | 1985 | 28.814827395932 |
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