Year | Value | 2022 | 51.137344459146 | 2021 | 51.173466147247 | 2020 | 51.166817338232 | 2019 | 51.171633488109 | 2018 | 51.18728708614 | 2017 | 51.206884855491 | 2016 | 51.22820855711 | 2015 | 51.252644510663 | 2014 | 51.272176809632 | 2013 | 51.284780300583 | 2012 | 51.300884054319 | 2011 | 51.322436272368 | 2010 | 51.341406827929 | 2009 | 51.360475167037 | 2008 | 51.37629152176 | 2007 | 51.38528650438 | 2006 | 51.394238860678 | 2005 | 51.40289443816 | 2004 | 51.413143722217 | 2003 | 51.420481187025 | 2002 | 51.422717566545 | 2001 | 51.425660323455 | 2000 | 51.415499126786 | 1999 | 51.389195887337 | 1998 | 51.362007014975 | 1997 | 51.339075471842 | 1996 | 51.320281530168 | 1995 | 51.300458673154 | 1994 | 51.278084202644 | 1993 | 51.255378994445 | 1992 | 51.228372814837 | 1991 | 51.197751762898 | 1990 | 51.163523118314 | 1989 | 51.123540023313 | 1988 | 51.084172199778 | 1987 | 51.047782673681 | 1986 | 51.016450674159 | 1985 | 50.988512545538 | 1984 | 50.957186853439 | 1983 | 50.923868003453 | 1982 | 50.893664900671 | 1981 | 50.861411368599 | 1980 | 50.832639207637 | 1979 | 50.80985129286 | 1978 | 50.786301585299 | 1977 | 50.766877636258 | 1976 | 50.754459250927 | 1975 | 50.738295638707 | 1974 | 50.718613654939 | 1973 | 50.700548920785 | 1972 | 50.679353618883 | 1971 | 50.658452810333 | 1970 | 50.636222555295 | 1969 | 50.606014533129 | 1968 | 50.578032480752 | 1967 | 50.559105053021 | 1966 | 50.540229508912 | 1965 | 50.535176833518 | 1964 | 50.538799211774 | 1963 | 50.536719677057 | 1962 | 50.536049433611 | 1961 | 50.558998078172 | 1960 | 50.611421888984 |
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