Year | Value | 2021 | 18.202066130026 | 2020 | 18.556419463037 | 2019 | 19.200197361365 | 2018 | 19.594324558647 | 2017 | 20.18131111658 | 2016 | 20.696461245491 | 2015 | 20.609303592563 | 2014 | 21.230833911908 | 2013 | 21.348918632754 | 2012 | 21.905433005044 | 2011 | 21.771369385899 | 2010 | 21.618528976463 | 2009 | 21.789574347603 | 2008 | 21.960156200165 | 2007 | 22.040822118669 | 2006 | 22.111324129767 | 2005 | 22.362442526249 | 2004 | 22.560771801664 | 2003 | 22.764575325113 | 2002 | 23.110340317958 | 2001 | 23.461324361675 | 2000 | 23.750021933679 | 1999 | 24.064027252813 | 1998 | 24.579441324023 | 1997 | 25.102110171246 | 1996 | 25.521258397542 | 1995 | 25.90897404743 | 1994 | 26.382004342352 | 1993 | 26.798845673003 | 1992 | 27.242773922278 | 1991 | 28.014927487184 | 1990 | 28.697823624918 | 1989 | 29.288281574279 | 1988 | 29.922025374299 | 1987 | 30.579504997597 | 1986 | 30.732239199864 | 1985 | 30.576053766013 | 1984 | 30.593432217248 | 1983 | 30.883517667759 | 1982 | 31.588470136976 | 1981 | 31.352396538643 | 1980 | 30.723849850909 | 1979 | 30.673928538094 | 1978 | 30.853749709626 | 1977 | 31.154635834139 | 1976 | 31.641775911994 | 1975 | 32.638793368168 | 1974 | 33.380046218218 | 1973 | 34.439540454796 | 1972 | 35.125741103642 | 1971 | 35.528103073994 | 1970 | 36.408513770627 | 1969 | 36.757736102057 | 1968 | 37.398191425317 | 1967 | 37.172955755452 | 1966 | 37.666515758852 | 1965 | 38.780838642793 | 1964 | 39.467060701236 | 1963 | 40.978132661023 | 1962 | 39.465643509924 | 1961 | 34.214715706851 | 1960 | 35.161699120312 |
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