| Year | Value | | 2021 | 78.479811622247 | | 2020 | 78.882959629216 | | 2019 | 78.863086992346 | | 2018 | 78.691811428467 | | 2017 | 78.375214302738 | | 2016 | 78.156763384182 | | 2015 | 77.91243950219 | | 2014 | 77.671342458404 | | 2013 | 77.424623021808 | | 2012 | 77.159712215388 | | 2011 | 76.877329914626 | | 2010 | 76.597771954507 | | 2009 | 76.398184837015 | | 2008 | 75.75465883575 | | 2007 | 75.881399858987 | | 2006 | 75.603394271461 | | 2005 | 75.247263924398 | | 2004 | 74.659924052193 | | 2003 | 74.641070798608 | | 2002 | 74.249798901078 | | 2001 | 73.924057596619 | | 2000 | 73.064753025822 | | 1999 | 72.625158360871 | | 1998 | 72.557062686727 | | 1997 | 72.025829211331 | | 1996 | 71.633548245651 | | 1995 | 71.416505584581 | | 1994 | 70.905005830312 | | 1993 | 70.719422692943 | | 1992 | 70.143551957267 | | 1991 | 69.565139094801 | | 1990 | 69.526418424184 | | 1989 | 69.354466602767 | | 1988 | 69.031155677301 | | 1987 | 68.726857257024 | | 1986 | 68.371724785131 | | 1985 | 67.979923371761 | | 1984 | 67.595639025756 | | 1983 | 67.216718827076 | | 1982 | 66.762461222721 | | 1981 | 66.267970851455 | | 1980 | 65.771484623929 | | 1979 | 65.206311376135 | | 1978 | 64.579410380775 | | 1977 | 63.886612621171 | | 1976 | 63.079405820976 | | 1975 | 62.273378274086 | | 1974 | 61.554790559071 | | 1973 | 60.80675597942 | | 1972 | 59.83282528885 | | 1971 | 59.196629688737 | | 1970 | 58.401369855405 | | 1969 | 57.660971696706 | | 1968 | 56.98607623746 | | 1967 | 56.489189914531 | | 1966 | 55.648336173316 | | 1965 | 54.725231071779 | | 1964 | 54.517684756661 | | 1963 | 53.776515774178 | | 1962 | 53.268072042637 | | 1961 | 45.043048904951 | | 1960 | 39.137440572888 |
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