| Year | Value | | 2021 | 68.58469608985 | | 2020 | 69.497656730308 | | 2019 | 71.919934875767 | | 2018 | 71.749175621977 | | 2017 | 71.634156365001 | | 2016 | 71.414401270464 | | 2015 | 71.474123529324 | | 2014 | 71.477672329241 | | 2013 | 71.202003218161 | | 2012 | 70.903149474712 | | 2011 | 70.674097507777 | | 2010 | 70.168137212764 | | 2009 | 70.286337231529 | | 2008 | 70.063935179155 | | 2007 | 69.782259752031 | | 2006 | 69.622940478627 | | 2005 | 69.401065245453 | | 2004 | 68.986885782534 | | 2003 | 68.692032652086 | | 2002 | 68.365976267098 | | 2001 | 68.077118632518 | | 2000 | 67.732918594411 | | 1999 | 67.527255669163 | | 1998 | 67.085720745003 | | 1997 | 66.775882095539 | | 1996 | 66.441429167389 | | 1995 | 66.033861087172 | | 1994 | 65.749759778196 | | 1993 | 65.309914338909 | | 1992 | 64.966830196356 | | 1991 | 64.646468087352 | | 1990 | 64.322458814453 | | 1989 | 64.150982634891 | | 1988 | 63.834663906839 | | 1987 | 63.398305992747 | | 1986 | 63.005430410007 | | 1985 | 62.449159949631 | | 1984 | 62.085888945612 | | 1983 | 61.677089391849 | | 1982 | 61.055106712646 | | 1981 | 60.748932724499 | | 1980 | 60.338842711703 | | 1979 | 59.907838932844 | | 1978 | 59.59710528406 | | 1977 | 59.297088309921 | | 1976 | 58.846885961401 | | 1975 | 58.635277998041 | | 1974 | 58.188083764344 | | 1973 | 57.818900014715 | | 1972 | 57.347580873732 | | 1971 | 56.965992832722 | | 1970 | 56.16985631168 | | 1969 | 56.129378794219 | | 1968 | 55.779575533719 | | 1967 | 55.45044928373 | | 1966 | 55.110844622499 | | 1965 | 54.663209097995 | | 1964 | 54.33305143211 | | 1963 | 53.878442322577 | | 1962 | 53.416338523843 | | 1961 | 52.9285262199 | | 1960 | 52.393067087532 |
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