Year | Value | 2021 | 14.250277055998 | 2020 | 14.746053969432 | 2019 | 15.239005180678 | 2018 | 15.733304013815 | 2017 | 16.226256569993 | 2016 | 16.719209126171 | 2015 | 17.212160337416 | 2014 | 17.706459170554 | 2013 | 18.199411726731 | 2012 | 18.692362937977 | 2011 | 19.185315494155 | 2010 | 19.678268050333 | 2009 | 20.17256688347 | 2008 | 20.665518094716 | 2007 | 21.158470650893 | 2006 | 21.249926028738 | 2005 | 21.364245251045 | 2004 | 21.431491852402 | 2003 | 20.745576518563 | 2002 | 20.933867002362 | 2001 | 20.375720211101 | 2000 | 20.321922930015 | 1999 | 20.254676328658 | 1998 | 20.468520520973 | 1997 | 20.472555317054 | 1996 | 20.486004637326 | 1995 | 20.617807975985 | 1994 | 20.779199819241 | 1993 | 20.815512983974 | 1992 | 20.921762614118 | 1991 | 21.23513177644 | 1990 | 21.383074299425 | 1989 | 21.746205946751 | 1988 | 21.726031966344 | 1987 | 21.738136354589 | 1986 | 22.105302797997 | 1985 | 22.153720350974 | 1984 | 22.191378447733 | 1983 | 22.25862504909 | 1982 | 22.325871650447 | 1981 | 22.527611454517 | 1980 | 22.662104657231 | 1979 | 22.729351258587 | 1978 | 22.863844461301 | 1977 | 22.998337664014 | 1976 | 23.132830866728 | 1975 | 22.25862504909 | 1974 | 21.855145440949 | 1973 | 21.30103344577 | 1972 | 20.980939623311 | 1971 | 20.644706616528 | 1970 | 20.308473609744 | 1969 | 19.969550738906 | 1968 | 19.740912294293 | 1967 | 19.445027248323 | 1966 | 19.149142202353 | 1965 | 18.921848689767 | 1964 | 18.691865313127 | 1963 | 18.46053700446 | 1962 | 18.231898559847 | 1961 | 18.003260115234 |
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