| Year | Value | | 2021 | 72.98969420675 | | 2020 | 73.112711218221 | | 2019 | 73.939309768062 | | 2018 | 73.842376964071 | | 2017 | 73.732319847466 | | 2016 | 73.228398539737 | | 2015 | 72.890280850134 | | 2014 | 72.730706845258 | | 2013 | 72.426248733385 | | 2012 | 72.341137045945 | | 2011 | 72.320357913425 | | 2010 | 72.087110656338 | | 2009 | 71.872887301113 | | 2008 | 71.45269053546 | | 2007 | 71.255523687785 | | 2006 | 70.89607739126 | | 2005 | 70.440063980353 | | 2004 | 70.135190562161 | | 2003 | 69.989859338799 | | 2002 | 69.940636021609 | | 2001 | 69.626613827571 | | 2000 | 69.306854033235 | | 1999 | 68.80754305039 | | 1998 | 67.922991018334 | | 1997 | 68.050657724552 | | 1996 | 67.742031364098 | | 1995 | 67.421049208872 | | 1994 | 67.399384912165 | | 1993 | 66.507028087104 | | 1992 | 65.518065498987 | | 1991 | 65.259270572903 | | 1990 | 65.230311136054 | | 1989 | 64.754691875376 | | 1988 | 63.419049274008 | | 1987 | 63.694716168956 | | 1986 | 63.76057057941 | | 1985 | 62.582531910777 | | 1984 | 61.859742272871 | | 1983 | 61.17476413654 | | 1982 | 60.452653848639 | | 1981 | 59.931305760677 | | 1980 | 59.334390761729 | | 1979 | 58.550602602725 | | 1978 | 57.824787099757 | | 1977 | 57.061732263234 | | 1976 | 55.863871917919 | | 1975 | 55.595636688315 | | 1974 | 54.931156539677 | | 1973 | 54.327061583026 | | 1972 | 53.542810732095 | | 1971 | 52.998430830277 | | 1970 | 52.100677293917 | | 1969 | 51.587272766051 | | 1968 | 51.150685050762 | | 1967 | 50.683989624215 | | 1966 | 50.158373006521 | | 1965 | 49.869992579264 | | 1964 | 49.508712564456 | | 1963 | 48.653043714261 | | 1962 | 47.969756526783 | | 1961 | 47.457472149707 | | 1960 | 46.741981701553 |
|