Year | Value | 2021 | 15.166 | 2020 | 13.976 | 2019 | 12.88 | 2018 | 12.963 | 2017 | 12.603 | 2016 | 12.411 | 2015 | 12.531 | 2014 | 12.576 | 2013 | 12.783 | 2012 | 12.691 | 2011 | 12.418 | 2010 | 12.347 | 2009 | 12.194 | 2008 | 12.318 | 2007 | 11.876 | 2006 | 11.587 | 2005 | 11.445 | 2004 | 11.633 | 2003 | 11.463 | 2002 | 11.409 | 2001 | 11.482 | 2000 | 11.188 | 1999 | 11.125 | 1998 | 11.062 | 1997 | 10.814 | 1996 | 10.652 | 1995 | 10.569 | 1994 | 10.73 | 1993 | 11.012 | 1992 | 10.975 | 1991 | 10.634 | 1990 | 10.499 | 1989 | 10.369 | 1988 | 10.157 | 1987 | 10.267 | 1986 | 9.998 | 1985 | 9.918 | 1984 | 10.067 | 1983 | 9.903 | 1982 | 9.783 | 1981 | 9.817 | 1980 | 10.044 | 1979 | 9.874 | 1978 | 9.988 | 1977 | 9.959 | 1976 | 10.127 | 1975 | 10.049 | 1974 | 10.13 | 1973 | 10.128 | 1972 | 10.247 | 1971 | 10.333 | 1970 | 10.521 | 1969 | 10.515 | 1968 | 10.691 | 1967 | 10.923 | 1966 | 10.931 | 1965 | 11.134 | 1964 | 11.62 | 1963 | 11.745 | 1962 | 12.09 | 1961 | 12.506 | 1960 | 12.684 |
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