Year | Value | 2021 | 13.389905552536 | 2020 | 13.48296371892 | 2019 | 13.760370455717 | 2018 | 14.2353664922 | 2017 | 14.602658973436 | 2016 | 15.521865175217 | 2015 | 15.875223911399 | 2014 | 15.909373355127 | 2013 | 15.734236364176 | 2012 | 15.652449034912 | 2011 | 15.27742997561 | 2010 | 15.261935617037 | 2009 | 15.273644732527 | 2008 | 15.120759138287 | 2007 | 14.539476650868 | 2006 | 13.917581301593 | 2005 | 13.593227638938 | 2004 | 13.647246655292 | 2003 | 13.285525130036 | 2002 | 13.167762060071 | 2001 | 13.087030525937 | 2000 | 13.033012563717 | 1999 | 13.076324780084 | 1998 | 13.59746943231 | 1997 | 13.804478210824 | 1996 | 14.284577564394 | 1995 | 14.807490950521 | 1994 | 15.13552644618 | 1993 | 15.477857439392 | 1992 | 16.418365634419 | 1991 | 17.459300829284 | 1990 | 18.171488124225 | 1989 | 18.9748585495 | 1988 | 20.071716530494 | 1987 | 20.860444687854 | 1986 | 21.1472324031 | 1985 | 20.837143626545 | 1984 | 21.066633413002 | 1983 | 21.320176667275 | 1982 | 20.727791213268 | 1981 | 20.495862400059 | 1980 | 20.513211680536 | 1979 | 20.562083420165 | 1978 | 20.888324248645 | 1977 | 20.878014940033 | 1976 | 20.972536448076 | 1975 | 21.007972386032 | 1974 | 21.097197116925 | 1973 | 20.972823817593 | 1972 | 21.036406940631 | 1971 | 20.957787607181 | 1970 | 20.602038205331 | 1969 | 20.480658370616 | 1968 | 20.528623705138 | 1967 | 20.83687398874 | 1966 | 21.513484669942 | 1965 | 22.243177319872 | 1964 | 23.239983513007 | 1963 | 24.611282780211 | 1962 | 25.866582358781 | 1961 | 26.918648437984 | 1960 | 27.725956438516 |
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