Year | Value | 2021 | 38.185378 | 2020 | 31.849211 | 2019 | 30.685844 | 2018 | 31.036317 | 2017 | 29.231317078 | 2016 | 26.901782890439 | 2015 | 27.370653580621 | 2014 | 33.402132 | 2013 | 32.728836 | 2012 | 28.526806506212 | 2011 | 32.201436246183 | 2010 | 28.504406874 | 2009 | 19.336 | 2008 | 22.002 | 2007 | 23.069 | 2006 | 21.89 | 2005 | 21.112 | 2004 | 23.213 | 2003 | 17.071 | 2002 | 24.176 | 2001 | 21.744 | 2000 | 22.322 | 1999 | 20.7000007629 | 1998 | 13.5 | 1997 | 15.6999998093 | 1996 | 18 | 1995 | 18 | 1994 | 17.2000007629 | 1993 | 14.6000003815 | 1992 | 16.1000003815 | 1991 | 15.6000003815 | 1990 | 14.8000001907 | 1989 | 14.8000001907 | 1988 | 12.8999996185 | 1987 | 9.3999996185 | 1986 | 9.5 | 1985 | 9.6000003815 | 1984 | 11.1999998093 | 1983 | 7.5 | 1982 | 8.8000001907 | 1981 | 8.8999996185 | 1980 | 8.6000003815 | 1979 | 8 | 1978 | 8.8000001907 | 1977 | 6.1999998093 | 1976 | 3.9000000954 | 1975 | 4.6999998093 |
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