Year | Value | 2021 | 17.347004145287 | 2020 | 17.347004145287 | 2019 | 17.347004145287 | 2018 | 17.35656798955 | 2017 | 17.35501080932 | 2016 | 17.365532188428 | 2015 | 17.405922810247 | 2014 | 17.395265646124 | 2013 | 17.395532257929 | 2012 | 17.381490003107 | 2011 | 17.377211618397 | 2010 | 17.371333562857 | 2009 | 17.373852729517 | 2008 | 17.344042590711 | 2007 | 17.320110507444 | 2006 | 17.290300368638 | 2005 | 17.302896201936 | 2004 | 17.27518536868 | 2003 | 16.754851495125 | 2002 | 16.733564536851 | 2001 | 16.840209258777 | 2000 | 16.803261481102 | 1999 | 16.681501759218 | 1998 | 16.721388564663 | 1997 | 16.66428745371 | 1996 | 16.641614953773 | 1995 | 16.647073148203 | 1994 | 16.643294398213 | 1993 | 16.316642454676 | 1992 | 16.317902038006 | 1991 | 16.215875788289 | 1990 | 16.238548288226 | 1989 | 16.273816621462 | 1988 | 16.297748704729 | 1987 | 16.281793982551 | 1986 | 16.243586621546 | 1985 | 16.395996204456 | 1984 | 16.630698564915 | 1983 | 16.492984120853 | 1982 | 16.419508426612 | 1981 | 16.446379537649 | 1980 | 18.402512448882 | 1979 | 18.398313837782 | 1978 | 18.407970643311 | 1977 | 18.403352171102 | 1976 | 18.482705920881 | 1975 | 18.370183143416 | 1974 | 18.614962170514 | 1973 | 18.601526614996 | 1972 | 19.060014947055 | 1971 | 19.075549808124 | 1970 | 18.564578837321 | 1969 | 18.559120642891 | 1968 | 18.559120642891 | 1967 | 18.579273976169 | 1966 | 18.544005642933 | 1965 | 18.544005642933 | 1964 | 18.542746059603 | 1963 | 18.688018003644 | 1962 | 18.851763836523 | 1961 | 19.091504530301 |
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