Year | Value | 2022 | 23.288753808612 | 2021 | 23.615723465926 | 2020 | 22.539037916724 | 2019 | 23.308361588882 | 2018 | 23.03546501537 | 2017 | 22.925700441264 | 2016 | 22.306728208536 | 2015 | 22.706905203983 | 2014 | 22.328258591354 | 2013 | 21.618496555428 | 2012 | 21.52864815835 | 2011 | 20.974694419194 | 2010 | 20.383058147071 | 2009 | 19.247765130119 | 2008 | 21.001655261754 | 2007 | 22.643325203818 | 2006 | 23.141969987329 | 2005 | 22.389421032348 | 2004 | 22.156931758407 | 2003 | 21.547815132759 | 2002 | 21.925004956038 | 2001 | 22.710522912569 | 2000 | 23.535357211545 | 1999 | 23.360581383417 | 1998 | 23.897981102326 | 1997 | 23.551544409426 | 1996 | 22.776205870854 | 1995 | 21.154833408988 | 1994 | 20.161136124352 | 1993 | 19.29765754701 | 1992 | 19.667582127595 | 1991 | 20.695257430727 | 1990 | 21.260669999889 | 1989 | 21.929632746245 | 1988 | 22.242862033198 | 1987 | 21.265441438831 | 1986 | 20.823472944766 | 1985 | 21.313949830701 | 1984 | 22.112045287851 | 1983 | 20.65852897558 | 1982 | 21.290477519924 | 1981 | 22.249000519284 | 1980 | 22.33437698264 | 1979 | 23.609624736382 | 1978 | 23.62676403682 | 1977 | 22.735344669852 | 1976 | 22.353909637779 | 1975 | 21.820217224867 |
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