| Year | Value | | 2021 | 72.824851212105 | | 2020 | 73.200460746774 | | 2019 | 73.330165921431 | | 2018 | 73.109479398212 | | 2017 | 72.628852850714 | | 2016 | 72.680971999177 | | 2015 | 72.519625440249 | | 2014 | 72.311505404532 | | 2013 | 72.049841638586 | | 2012 | 71.822923708648 | | 2011 | 71.60741541647 | | 2010 | 71.350355188472 | | 2009 | 71.107692805177 | | 2008 | 70.640135240372 | | 2007 | 70.629194600517 | | 2006 | 70.407544761649 | | 2005 | 70.058274297816 | | 2004 | 69.572444602904 | | 2003 | 69.439501208013 | | 2002 | 69.04922619673 | | 2001 | 68.681289559397 | | 2000 | 68.312504740394 | | 1999 | 67.990942490434 | | 1998 | 67.647892347424 | | 1997 | 67.314418750987 | | 1996 | 66.922563268048 | | 1995 | 66.626881267274 | | 1994 | 66.369599276272 | | 1993 | 66.010291365212 | | 1992 | 65.64170324782 | | 1991 | 65.169207923746 | | 1990 | 64.788559678804 | | 1989 | 64.53015469423 | | 1988 | 64.207545518561 | | 1987 | 63.949587809415 | | 1986 | 63.605279763647 | | 1985 | 63.298664364842 | | 1984 | 62.923400573961 | | 1983 | 62.517486190778 | | 1982 | 62.126809767743 | | 1981 | 61.65684549499 | | 1980 | 61.153525497581 | | 1979 | 60.619214386221 | | 1978 | 60.01443573086 | | 1977 | 59.429835462132 | | 1976 | 58.726143196077 | | 1975 | 57.885005466777 | | 1974 | 57.093803682491 | | 1973 | 56.533949492808 | | 1972 | 55.608272899511 | | 1971 | 55.039148500434 | | 1970 | 54.148192594739 | | 1969 | 53.456456257534 | | 1968 | 52.735554815873 | | 1967 | 52.269711170804 | | 1966 | 51.375194635169 | | 1965 | 50.015083942668 | | 1964 | 50.318374838932 | | 1963 | 49.612903542007 | | 1962 | 49.12405861307 | | 1961 | 41.689084654273 | | 1960 | 36.301221418479 |
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