Year | Value | 2021 | 20.625753633306 | 2020 | 20.625753633306 | 2019 | 20.625753633306 | 2018 | 20.625753633306 | 2017 | 20.625753633306 | 2016 | 20.625753633306 | 2015 | 20.625753633306 | 2014 | 20.625753633306 | 2013 | 20.625753633306 | 2012 | 20.625753633306 | 2011 | 20.625753633306 | 2010 | 20.51998053775 | 2009 | 19.701296778152 | 2008 | 19.595523682596 | 2007 | 19.489750587041 | 2006 | 19.489750587041 | 2005 | 19.489750587041 | 2004 | 19.483404201307 | 2003 | 19.377631105752 | 2002 | 19.377631105752 | 2001 | 19.377631105752 | 2000 | 19.377631105752 | 1999 | 19.377631105752 | 1998 | 19.377631105752 | 1997 | 19.377631105752 | 1996 | 19.377631105752 | 1995 | 19.377631105752 | 1994 | 19.377631105752 | 1993 | 19.377631105752 | 1992 | 19.377631105752 | 1991 | 19.356476486641 | 1990 | 19.398785724863 | 1989 | 19.441094963085 | 1988 | 19.483404201307 | 1987 | 19.483404201307 | 1986 | 19.52571343953 | 1985 | 19.377631105752 | 1984 | 19.271858010196 | 1983 | 19.166084914641 | 1982 | 19.060311819086 | 1981 | 18.95453872353 | 1980 | 18.891074866197 | 1979 | 18.852996551797 | 1978 | 18.34317023122 | 1977 | 18.28605275962 | 1976 | 18.002580863532 | 1975 | 17.759302743754 | 1974 | 17.516024623977 | 1973 | 17.262169194644 | 1972 | 17.124664170422 | 1971 | 16.982928222377 | 1970 | 16.877155126822 | 1969 | 16.860231431533 | 1968 | 16.754458335978 | 1967 | 16.648685240422 | 1966 | 16.500602906645 | 1965 | 16.373675191978 | 1964 | 16.246747477312 | 1963 | 16.119819762645 | 1962 | 16.01404666709 | 1961 | 15.887118952423 |
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