Year | Value | 2021 | 9.6 | 2020 | 9.8 | 2019 | 10.1 | 2018 | 10.9 | 2017 | 11.5 | 2016 | 12.9 | 2015 | 13.3 | 2014 | 13.3 | 2013 | 13.2 | 2012 | 13.3 | 2011 | 12.6 | 2010 | 12.5 | 2009 | 12.3 | 2008 | 12 | 2007 | 11.3 | 2006 | 10.3 | 2005 | 10.2 | 2004 | 10.4 | 2003 | 10.2 | 2002 | 9.7 | 2001 | 9 | 2000 | 8.7 | 1999 | 8.3 | 1998 | 8.8 | 1997 | 8.6 | 1996 | 8.9 | 1995 | 9.3 | 1994 | 9.5 | 1993 | 9.4 | 1992 | 10.7 | 1991 | 12.1 | 1990 | 13.4 | 1989 | 14.6 | 1988 | 16 | 1987 | 17.2 | 1986 | 17.2 | 1985 | 16.6 | 1984 | 16.9 | 1983 | 17.5 | 1982 | 16.6 | 1981 | 16 | 1980 | 15.9 | 1979 | 15.8 | 1978 | 16.358 | 1977 | 16.31 | 1976 | 16.219 | 1975 | 16.079 | 1974 | 15.944 | 1973 | 15.637 | 1972 | 15.507 | 1971 | 15.23 | 1970 | 14.725 | 1969 | 14.512 | 1968 | 14.495 | 1967 | 14.828 | 1966 | 15.444 | 1965 | 16.211 | 1964 | 17.436 | 1963 | 19.1 | 1962 | 20.708 | 1961 | 22.146 | 1960 | 23.328 |
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