Year | Value | 2021 | 9.283 | 2020 | 9.47 | 2019 | 9.3 | 2018 | 9.9 | 2017 | 10.8 | 2016 | 12.4 | 2015 | 12.5 | 2014 | 12.5 | 2013 | 12.5 | 2012 | 12.2 | 2011 | 11.5 | 2010 | 11.4 | 2009 | 11.4 | 2008 | 11.1 | 2007 | 10.7 | 2006 | 9.9 | 2005 | 9.3 | 2004 | 9.1 | 2003 | 9 | 2002 | 8.9 | 2001 | 9.2 | 2000 | 9.4 | 1999 | 9.3 | 1998 | 9.2 | 1997 | 8.9 | 1996 | 9.4 | 1995 | 9.9 | 1994 | 10.8 | 1993 | 11.5 | 1992 | 12.5 | 1991 | 13 | 1990 | 14 | 1989 | 15.1 | 1988 | 16.1 | 1987 | 16.1 | 1986 | 17.1 | 1985 | 16.5 | 1984 | 17 | 1983 | 17.6 | 1982 | 16.3 | 1981 | 16.3 | 1980 | 16.34 | 1979 | 16.228 | 1978 | 16.17 | 1977 | 16.026 | 1976 | 15.885 | 1975 | 15.738 | 1974 | 15.998 | 1973 | 15.816 | 1972 | 16.185 | 1971 | 16.412 | 1970 | 16.281 | 1969 | 15.948 | 1968 | 16.278 | 1967 | 16.631 | 1966 | 17.06 | 1965 | 17.88 | 1964 | 19.162 | 1963 | 21.15 | 1962 | 22.771 | 1961 | 23.834 | 1960 | 24.389 |
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