Year | Value | 2021 | 17.055281882868 | 2020 | 17.055281882868 | 2019 | 17.12096332786 | 2018 | 17.159277504105 | 2017 | 17.19759168035 | 2016 | 17.235905856596 | 2015 | 17.274220032841 | 2014 | 17.312534209086 | 2013 | 17.350848385331 | 2012 | 17.389162561576 | 2011 | 17.427476737822 | 2010 | 17.465790914067 | 2009 | 17.504105090312 | 2008 | 17.810618500274 | 2007 | 18.128078817734 | 2006 | 18.445539135194 | 2005 | 18.762999452655 | 2004 | 19.080459770115 | 2003 | 19.397920087575 | 2002 | 19.715380405036 | 2001 | 20.032840722496 | 2000 | 20.350301039956 | 1999 | 20.667761357416 | 1998 | 20.985221674877 | 1997 | 21.302681992337 | 1996 | 21.620142309798 | 1995 | 21.937602627258 | 1994 | 22.255062944718 | 1993 | 22.572523262178 | 1992 | 22.889983579639 | 1991 | 23.207443897099 | 1990 | 22.441160372195 | 1989 | 21.620142309798 | 1988 | 20.7991242474 | 1987 | 19.978106185003 | 1986 | 19.157088122605 | 1985 | 18.88341543514 | 1984 | 18.062397372742 | 1983 | 17.515051997811 | 1982 | 16.967706622879 | 1981 | 16.420361247948 | 1980 | 15.873015873016 | 1979 | 15.59934318555 | 1978 | 15.325670498084 | 1977 | 14.778325123153 | 1976 | 14.230979748221 | 1975 | 13.409961685824 | 1974 | 13.136288998358 | 1973 | 12.862616310892 | 1972 | 12.588943623426 | 1971 | 12.096332785988 | 1970 | 12.096332785988 | 1969 | 12.096332785988 | 1968 | 11.986863711002 | 1967 | 12.096332785988 | 1966 | 12.205801860974 | 1965 | 12.205801860974 | 1964 | 12.47947454844 | 1963 | 12.47947454844 | 1962 | 12.424740010947 | 1961 | 12.424740010947 |
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