Year | Value | 2021 | 34.797297297297 | 2020 | 34.797297297297 | 2019 | 34.797297297297 | 2018 | 34.797297297297 | 2017 | 34.435328185328 | 2016 | 34.034749034749 | 2015 | 33.63416988417 | 2014 | 33.233590733591 | 2013 | 32.833011583012 | 2012 | 32.432432432432 | 2011 | 32.031853281853 | 2010 | 31.631274131274 | 2009 | 31.230694980695 | 2008 | 30.830115830116 | 2007 | 30.429536679537 | 2006 | 29.150579150579 | 2005 | 29.324324324324 | 2004 | 29.512548262548 | 2003 | 29.700772200772 | 2002 | 29.888996138996 | 2001 | 30.07722007722 | 2000 | 30.265444015444 | 1999 | 30.453667953668 | 1998 | 28.957528957529 | 1997 | 27.26833976834 | 1996 | 27.26833976834 | 1995 | 28.088803088803 | 1994 | 28.185328185328 | 1993 | 28.281853281853 | 1992 | 28.378378378378 | 1991 | 27.26833976834 | 1990 | 26.544401544401 | 1989 | 26.061776061776 | 1988 | 26.061776061776 | 1987 | 25.096525096525 | 1986 | 25.096525096525 | 1985 | 24.131274131274 | 1984 | 23.166023166023 | 1983 | 22.683397683398 | 1982 | 23.117760617761 | 1981 | 24.903474903475 | 1980 | 26.930501930502 | 1979 | 27.027027027027 | 1978 | 24.855212355212 | 1977 | 22.92471042471 | 1976 | 22.92471042471 | 1975 | 23.405275779376 | 1974 | 23.405275779376 | 1973 | 23.405275779376 | 1972 | 23.405275779376 | 1971 | 23.405275779376 | 1970 | 21.58273381295 | 1969 | 21.822541966427 | 1968 | 21.966426858513 | 1967 | 22.254196642686 | 1966 | 22.541966426859 | 1965 | 22.829736211031 | 1964 | 23.117505995204 | 1963 | 23.405275779376 | 1962 | 23.405275779376 | 1961 | 23.405275779376 |
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