Year | Value | 2021 | 5 | 2020 | 5.8 | 2019 | 7 | 2018 | 7.2 | 2017 | 7.6 | 2016 | 8.3 | 2015 | 8.2 | 2014 | 8.6 | 2013 | 8 | 2012 | 12.8 | 2011 | 13.5 | 2010 | 12.6 | 2009 | 11.8 | 2008 | 11.3 | 2007 | 10.2 | 2006 | 9.6 | 2005 | 8.4 | 2004 | 7.2 | 2003 | 6.9 | 2002 | 7.1 | 2001 | 7.2 | 2000 | 8.1 | 1999 | 7.8 | 1998 | 8.1 | 1997 | 9.1 | 1996 | 9.9 | 1995 | 11.2 | 1994 | 11.9 | 1993 | 12 | 1992 | 12.3 | 1991 | 12 | 1990 | 12 | 1989 | 12.3 | 1988 | 13.4 | 1987 | 12.6 | 1986 | 13 | 1985 | 14 | 1984 | 14.4 | 1983 | 15.6 | 1982 | 16.4 | 1981 | 16.8 | 1980 | 17 | 1979 | 16.8 | 1978 | 17.3 | 1977 | 17.5 | 1976 | 17.4 | 1975 | 17.9 | 1974 | 19.1 | 1973 | 19.4 | 1972 | 19.5 | 1971 | 19.7 | 1970 | 20 | 1969 | 21.3 | 1968 | 21.7 | 1967 | 23.7 | 1966 | 25.3 | 1965 | 28.1 | 1964 | 30.7 | 1963 | 33.5 | 1962 | 34 | 1961 | 35 | 1960 | 35.725 |
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