| Year | Value | | 2021 | 67.500892545839 | | 2020 | 68.278831857064 | | 2019 | 69.968525582402 | | 2018 | 69.633171895947 | | 2017 | 69.415472021209 | | 2016 | 68.800236024754 | | 2015 | 68.452374163972 | | 2014 | 68.097750539608 | | 2013 | 67.892178554263 | | 2012 | 67.421038543474 | | 2011 | 66.918623418205 | | 2010 | 66.414471138559 | | 2009 | 66.014513277849 | | 2008 | 65.305497086552 | | 2007 | 64.907283835094 | | 2006 | 64.322175901636 | | 2005 | 63.533356128851 | | 2004 | 63.469550355338 | | 2003 | 63.144113960136 | | 2002 | 63.03333873013 | | 2001 | 62.913029225245 | | 2000 | 62.744670253439 | | 1999 | 62.753834688057 | | 1998 | 63.250527917594 | | 1997 | 62.778704849651 | | 1996 | 62.05245177723 | | 1995 | 61.230320539681 | | 1994 | 61.066402362448 | | 1993 | 61.384249050641 | | 1992 | 62.809001236388 | | 1991 | 63.999886349232 | | 1990 | 64.289259698613 | | 1989 | 64.514743241084 | | 1988 | 64.526362337468 | | 1987 | 64.605857781425 | | 1986 | 64.399838834548 | | 1985 | 63.114110870646 | | 1984 | 62.466520727397 | | 1983 | 62.569083635124 | | 1982 | 62.484125213652 | | 1981 | 62.065474748104 | | 1980 | 61.809083937556 | | 1979 | 61.549390429931 | | 1978 | 61.666391307698 | | 1977 | 61.570475364871 | | 1976 | 61.709367634121 | | 1975 | 61.719936666356 | | 1974 | 61.9445551071 | | 1973 | 61.951502119229 | | 1972 | 61.799078398438 | | 1971 | 61.680146298089 | | 1970 | 61.457252756592 | | 1969 | 60.929596599594 | | 1968 | 61.292628922869 | | 1967 | 61.339965189264 | | 1966 | 61.508952291004 | | 1965 | 61.513554291077 | | 1964 | 61.734300058255 | | 1963 | 61.236625631519 | | 1962 | 60.813022237202 | | 1961 | 60.90656827653 | | 1960 | 60.682670873569 |
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