| Year | Value | | 2021 | 72.315052195592 | | 2020 | 72.358943590438 | | 2019 | 72.803286289106 | | 2018 | 72.841634799696 | | 2017 | 72.863571383345 | | 2016 | 72.923677130932 | | 2015 | 72.990217275856 | | 2014 | 73.001629001279 | | 2013 | 73.225273041093 | | 2012 | 73.24948515428 | | 2011 | 73.326477594059 | | 2010 | 73.338846757295 | | 2009 | 73.369254762399 | | 2008 | 73.521391237453 | | 2007 | 73.632752548962 | | 2006 | 73.663122527996 | | 2005 | 73.291667844231 | | 2004 | 73.436353194267 | | 2003 | 73.501270183771 | | 2002 | 84.086030331892 | | 2001 | 84.093474247525 | | 2000 | 84.313515268057 | | 1999 | 84.192024190642 | | 1998 | 83.448860685175 | | 1997 | 83.293119463594 | | 1996 | 76.558119416659 | | 1995 | 76.558119416659 | | 1994 | 76.558119416659 | | 1993 | 76.981399500207 | | 1992 | 79.86745881796 | | 1991 | 81.508880821338 | | 1990 | 81.202568211259 | | 1989 | 81.122435798496 | | 1988 | 80.92985951621 | | 1987 | 80.70691046457 | | 1986 | 80.475560434172 | | 1985 | 80.511749265742 | | 1984 | 80.524673848446 | | 1983 | 80.763132399331 | | 1982 | 80.471683059361 | | 1981 | 80.46780568455 | | 1980 | 80.511749265742 | | 1979 | 80.593174136776 | | 1978 | 81.371234015543 | | 1977 | 81.408715305384 | | 1976 | 81.1353603812 | | 1975 | 90.913453425738 | | 1974 | 90.913453425738 | | 1973 | 90.913453425738 | | 1972 | 90.913453425738 | | 1971 | 90.913453425738 | | 1970 | 90.914099654873 | | 1969 | 90.893420322547 | | 1968 | 90.913453425738 | | 1967 | 90.913453425738 | | 1966 | 90.913453425738 | | 1965 | 90.913453425738 | | 1964 | 90.912160967468 | | 1963 | 90.913453425738 | | 1962 | 90.913453425738 | | 1961 | 90.913453425738 |
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