Year | Value | 2021 | 8.676 | 2020 | 8.176 | 2019 | 7.953 | 2018 | 7.998 | 2017 | 8.014 | 2016 | 8.161 | 2015 | 8.181 | 2014 | 8.243 | 2013 | 8.376 | 2012 | 8.486 | 2011 | 8.762 | 2010 | 17.738 | 2009 | 8.695 | 2008 | 8.853 | 2007 | 8.937 | 2006 | 9.084 | 2005 | 9.239 | 2004 | 10.184 | 2003 | 9.689 | 2002 | 10.023 | 2001 | 10.239 | 2000 | 10.341 | 1999 | 10.564 | 1998 | 11.023 | 1997 | 11.396 | 1996 | 11.648 | 1995 | 12.041 | 1994 | 12.619 | 1993 | 12.881 | 1992 | 13.278 | 1991 | 13.654 | 1990 | 14.029 | 1989 | 14.245 | 1988 | 14.401 | 1987 | 14.704 | 1986 | 14.976 | 1985 | 15.233 | 1984 | 15.523 | 1983 | 15.732 | 1982 | 15.969 | 1981 | 16.148 | 1980 | 16.374 | 1979 | 16.506 | 1978 | 16.641 | 1977 | 16.748 | 1976 | 16.857 | 1975 | 16.975 | 1974 | 17.092 | 1973 | 17.216 | 1972 | 17.437 | 1971 | 17.632 | 1970 | 17.931 | 1969 | 18.259 | 1968 | 18.584 | 1967 | 18.911 | 1966 | 19.351 | 1965 | 19.601 | 1964 | 19.94 | 1963 | 21.605 | 1962 | 20.552 | 1961 | 20.887 | 1960 | 21.263 |
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