| Year | Value | | 2021 | 70.744976174107 | | 2020 | 72.288226584108 | | 2019 | 73.126844983844 | | 2018 | 72.878992108321 | | 2017 | 72.604603069564 | | 2016 | 72.280130707134 | | 2015 | 71.931308708353 | | 2014 | 71.580152101742 | | 2013 | 71.241556014266 | | 2012 | 70.808909965331 | | 2011 | 70.381568445632 | | 2010 | 69.924689583927 | | 2009 | 69.570289369487 | | 2008 | 69.038246279232 | | 2007 | 68.812939891412 | | 2006 | 68.461778563113 | | 2005 | 67.964040142013 | | 2004 | 67.434351302053 | | 2003 | 67.196708214594 | | 2002 | 66.833954916203 | | 2001 | 66.400141513688 | | 2000 | 66.039396270069 | | 1999 | 65.670605143352 | | 1998 | 65.190628966783 | | 1997 | 64.762259172621 | | 1996 | 64.292702150366 | | 1995 | 64.010507213403 | | 1994 | 63.614760904826 | | 1993 | 63.398296315557 | | 1992 | 63.133587407108 | | 1991 | 62.645296612889 | | 1990 | 62.337259833828 | | 1989 | 61.948389699344 | | 1988 | 61.531828236325 | | 1987 | 61.06357489746 | | 1986 | 60.477631824796 | | 1985 | 59.984451731716 | | 1984 | 59.477041292189 | | 1983 | 58.925421312622 | | 1982 | 58.464410991139 | | 1981 | 57.903288154226 | | 1980 | 57.33628380058 | | 1979 | 56.715663100012 | | 1978 | 56.032214617454 | | 1977 | 55.42070435365 | | 1976 | 54.68218751053 | | 1975 | 54.079705447331 | | 1974 | 53.623524504533 | | 1973 | 53.164398780307 | | 1972 | 52.655971322948 | | 1971 | 51.330100721438 | | 1970 | 51.381036596303 | | 1969 | 51.43750870871 | | 1968 | 50.994091595041 | | 1967 | 49.951576125064 | | 1966 | 49.24099004465 | | 1965 | 48.407623167977 | | 1964 | 49.145190497995 | | 1963 | 48.618115908898 | | 1962 | 48.234905453618 | | 1961 | 47.810222957205 | | 1960 | 47.321977224462 |
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