| Year | Value | | 2022 | 46.699738618652 | | 2021 | 46.270954448875 | | 2020 | 45.866006026617 | | 2019 | 45.466407579835 | | 2018 | 45.060713020845 | | 2017 | 44.661480964151 | | 2016 | 44.267907241577 | | 2015 | 43.866620798977 | | 2014 | 43.456298826572 | | 2013 | 43.065321714362 | | 2012 | 42.692877817958 | | 2011 | 42.334350511853 | | 2010 | 41.971542731583 | | 2009 | 41.593139581186 | | 2008 | 41.209166134462 | | 2007 | 40.825089650626 | | 2006 | 40.445059749166 | | 2005 | 40.065276140709 | | 2004 | 39.698847317416 | | 2003 | 39.34094531307 | | 2002 | 38.989117491213 | | 2001 | 38.635066141653 | | 2000 | 38.312462087246 | | 1999 | 37.979355043314 | | 1998 | 37.647622521705 | | 1997 | 37.312568554435 | | 1996 | 36.983140425387 | | 1995 | 36.653781708663 | | 1994 | 36.297152068283 | | 1993 | 35.942457815714 | | 1992 | 35.606745448986 | | 1991 | 35.257094999686 | | 1990 | 34.881042566873 | | 1989 | 34.430619376227 | | 1988 | 34.018546572141 | | 1987 | 33.608839621511 | | 1986 | 33.196085069822 | | 1985 | 32.769487827314 | | 1984 | 32.341396929178 | | 1983 | 31.917447274143 | | 1982 | 31.501982292806 | | 1981 | 31.092171109656 | | 1980 | 30.60622759801 | | 1979 | 30.123693291929 | | 1978 | 29.658728933721 | | 1977 | 29.195112506055 | | 1976 | 28.736712174127 | | 1975 | 28.277856906864 | | 1974 | 27.947033560002 | | 1973 | 27.501353363229 | | 1972 | 27.062058948142 | | 1971 | 26.618285635489 | | 1970 | 26.229362903306 | | 1969 | 25.871434906536 | | 1968 | 25.519462078774 | | 1967 | 25.169385518496 | | 1966 | 24.815996789508 | | 1965 | 24.466165085067 | | 1964 | 24.124120349439 | | 1963 | 23.788624321408 | | 1962 | 23.459351619268 | | 1961 | 23.134766482259 | | 1960 | 22.846778813138 |
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