| Year | Value | | 2021 | 43.282828282828 | | 2020 | 43.282828282828 | | 2019 | 43.282828282828 | | 2018 | 43.282828282828 | | 2017 | 46.565656565657 | | 2016 | 46.919191919192 | | 2015 | 46.767676767677 | | 2014 | 48.080808080808 | | 2013 | 47.777777777778 | | 2012 | 48.282828282828 | | 2011 | 48.535353535354 | | 2010 | 46.010101010101 | | 2009 | 44.444444444444 | | 2008 | 40.909090909091 | | 2007 | 41.414141414141 | | 2006 | 42.424242424242 | | 2005 | 38.383838383838 | | 2004 | 37.878787878788 | | 2003 | 37.373737373737 | | 2002 | 37.373737373737 | | 2001 | 37.878787878788 | | 2000 | 39.89898989899 | | 1999 | 39.89898989899 | | 1998 | 40.40404040404 | | 1997 | 40.909090909091 | | 1996 | 42.424242424242 | | 1995 | 42.424242424242 | | 1994 | 42.424242424242 | | 1993 | 42.424242424242 | | 1992 | 42.929292929293 | | 1991 | 42.929292929293 | | 1990 | 42.929292929293 | | 1989 | 42.929292929293 | | 1988 | 42.929292929293 | | 1987 | 43.434343434343 | | 1986 | 43.434343434343 | | 1985 | 43.434343434343 | | 1984 | 43.434343434343 | | 1983 | 43.434343434343 | | 1982 | 43.939393939394 | | 1981 | 43.939393939394 | | 1980 | 43.939393939394 | | 1979 | 43.939393939394 | | 1978 | 43.939393939394 | | 1977 | 44.444444444444 | | 1976 | 44.444444444444 | | 1975 | 44.444444444444 | | 1974 | 44.444444444444 | | 1973 | 44.444444444444 | | 1972 | 44.949494949495 | | 1971 | 44.949494949495 | | 1970 | 44.949494949495 | | 1969 | 44.949494949495 | | 1968 | 45.454545454546 | | 1967 | 45.454545454546 | | 1966 | 45.454545454546 | | 1965 | 45.454545454546 | | 1964 | 45.454545454546 | | 1963 | 45.454545454546 | | 1962 | 45.454545454546 | | 1961 | 45.454545454546 |
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