| Year | Value | | 2022 | 63.538154438421 | | 2021 | 63.151701620205 | | 2020 | 62.899531250347 | | 2019 | 62.613725182068 | | 2018 | 62.193411868761 | | 2017 | 61.734566429564 | | 2016 | 61.185338439723 | | 2015 | 60.546254629361 | | 2014 | 59.859425963949 | | 2013 | 59.184027975763 | | 2012 | 58.576507520945 | | 2011 | 57.98889955249 | | 2010 | 57.380940308464 | | 2009 | 56.694688783309 | | 2008 | 55.849790235039 | | 2007 | 54.898274830525 | | 2006 | 53.922188604812 | | 2005 | 53.081601717466 | | 2004 | 52.392260856851 | | 2003 | 51.800395886594 | | 2002 | 51.221746654449 | | 2001 | 50.664642146316 | | 2000 | 50.112612649477 | | 1999 | 49.565867188621 | | 1998 | 49.031410961719 | | 1997 | 48.521906528024 | | 1996 | 48.031485072787 | | 1995 | 47.576455994823 | | 1994 | 47.128090709064 | | 1993 | 46.699605653295 | | 1992 | 46.302345114939 | | 1991 | 45.845292828894 | | 1990 | 45.104695385152 | | 1989 | 44.34136853728 | | 1988 | 43.600952530003 | | 1987 | 42.840289869499 | | 1986 | 42.103425213795 | | 1985 | 41.435233529099 | | 1984 | 40.813840178249 | | 1983 | 40.22858844319 | | 1982 | 39.679000027722 | | 1981 | 39.06808724289 | | 1980 | 38.479339524247 | | 1979 | 37.908252349521 | | 1978 | 37.383681114824 | | 1977 | 36.879513868939 | | 1976 | 36.380026500871 | | 1975 | 35.832516818223 | | 1974 | 35.28395758585 | | 1973 | 34.730501388137 | | 1972 | 34.211280174071 | | 1971 | 33.616351071446 | | 1970 | 32.986549472709 | | 1969 | 32.394204565566 | | 1968 | 31.823154309686 | | 1967 | 31.281223003643 | | 1966 | 30.750096842631 | | 1965 | 30.153084057489 | | 1964 | 29.557816456366 | | 1963 | 29.015578298148 | | 1962 | 28.539599884572 | | 1961 | 28.088756014029 | | 1960 | 27.673787998766 |
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