| Year | Value | | 2022 | 43.100920471115 | | 2021 | 43.5234883802 | | 2020 | 43.938245864986 | | 2019 | 44.372089468038 | | 2018 | 44.814763271857 | | 2017 | 45.26320103594 | | 2016 | 45.715712947471 | | 2015 | 46.174192808065 | | 2014 | 46.636509991345 | | 2013 | 47.091907009987 | | 2012 | 47.539158477376 | | 2011 | 47.978275272016 | | 2010 | 48.423706251434 | | 2009 | 48.912991390689 | | 2008 | 49.411600701561 | | 2007 | 49.918105613873 | | 2006 | 50.411685164097 | | 2005 | 50.911914481849 | | 2004 | 51.417065629213 | | 2003 | 51.91602434827 | | 2002 | 52.407377293749 | | 2001 | 52.896954876521 | | 2000 | 53.342142284802 | | 1999 | 53.722530340355 | | 1998 | 54.093879319695 | | 1997 | 54.46279501657 | | 1996 | 54.825379559495 | | 1995 | 55.182777243439 | | 1994 | 55.543149323175 | | 1993 | 55.904721679655 | | 1992 | 56.263313368749 | | 1991 | 56.627972223468 | | 1990 | 56.996090621587 | | 1989 | 57.355541173354 | | 1988 | 57.712207538107 | | 1987 | 58.079135269049 | | 1986 | 58.446067334966 | | 1985 | 58.810171289729 | | 1984 | 59.168157399285 | | 1983 | 59.523521976162 | | 1982 | 59.866357113775 | | 1981 | 60.244840541216 | | 1980 | 60.669862294853 | | 1979 | 61.084458822547 | | 1978 | 61.488166951399 | | 1977 | 61.823819996638 | | 1976 | 62.090005688204 | | 1975 | 62.350586683552 | | 1974 | 62.582186216578 | | 1973 | 62.846571598304 | | 1972 | 63.079825720316 | | 1971 | 63.292871053 | | 1970 | 63.494215893266 | | 1969 | 63.684170902167 | | 1968 | 63.880901883978 | | 1967 | 64.088666692753 | | 1966 | 64.301410395646 | | 1965 | 64.500478696139 | | 1964 | 64.717881744252 | | 1963 | 65.102013141706 | | 1962 | 65.47888043824 | | 1961 | 65.910434692009 | | 1960 | 66.397483996927 |
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