Year | Value | 2021 | 6.954356846473 | 2020 | 7.6683720930233 | 2019 | 8.3434053156146 | 2018 | 9.0184219269103 | 2017 | 9.693438538206 | 2016 | 9.7040199335548 | 2015 | 9.5185714285714 | 2014 | 9.8763289036545 | 2013 | 10.234069767442 | 2012 | 7.9439700996678 | 2011 | 7.3482392026578 | 2010 | 7.2591362126246 | 2009 | 11.09634551495 | 2008 | 12.45122923588 | 2007 | 12.263936877076 | 2006 | 12.581445182724 | 2005 | 12.527558139535 | 2004 | 12.275382059801 | 2003 | 12.042674418605 | 2002 | 12.256328903655 | 2001 | 11.778887043189 | 2000 | 11.829418604651 | 1999 | 9.2358471760797 | 1998 | 12.973006644518 | 1997 | 12.713156146179 | 1996 | 12.953571428571 | 1995 | 13.776196013289 | 1994 | 12.264053156146 | 1993 | 17.275747508306 | 1992 | 17.275747508306 | 1991 | 17.607973421927 | 1990 | 18.106312292359 | 1989 | 18.43853820598 | 1988 | 18.272425249169 | 1987 | 18.106312292359 | 1986 | 17.940199335548 | 1985 | 17.774086378738 | 1984 | 17.940199335548 | 1983 | 17.940199335548 | 1982 | 17.940199335548 | 1981 | 17.940199335548 | 1980 | 17.275747508306 | 1979 | 17.275747508306 | 1978 | 17.275747508306 | 1977 | 17.109634551495 | 1976 | 17.109634551495 | 1975 | 17.109634551495 | 1974 | 17.109634551495 | 1973 | 16.943521594684 | 1972 | 16.943521594684 | 1971 | 16.943521594684 | 1970 | 16.943521594684 | 1969 | 16.777408637874 | 1968 | 16.777408637874 | 1967 | 16.777408637874 | 1966 | 16.777408637874 | 1965 | 16.611295681063 | 1964 | 16.611295681063 | 1963 | 16.611295681063 | 1962 | 16.611295681063 | 1961 | 16.611295681063 |
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