Year | Value | 2021 | 29 | 2020 | 28.7 | 2019 | 28.4 | 2018 | 28.1 | 2017 | 27.8 | 2016 | 27.5 | 2015 | 27.2 | 2014 | 26.9 | 2013 | 26.6 | 2012 | 26.3 | 2011 | 26 | 2010 | 25.7 | 2009 | 25.4 | 2008 | 25.1 | 2007 | 24.8 | 2006 | 24.5 | 2005 | 24.2 | 2004 | 23.9 | 2003 | 23.6 | 2002 | 23.3 | 2001 | 23 | 2000 | 22.7 | 1999 | 22.36 | 1998 | 22.02 | 1997 | 21.68 | 1996 | 21.34 | 1995 | 21 | 1994 | 20.66 | 1993 | 20.32 | 1992 | 19.98 | 1991 | 19.64 | 1990 | 19.3 | 1989 | 19.3 | 1988 | 19.3 | 1987 | 19.3 | 1986 | 19.3 | 1985 | 19.3 | 1984 | 19.3 | 1983 | 19.3 | 1982 | 19.3 | 1981 | 19.3 | 1980 | 19.3 | 1979 | 19.3 | 1978 | 19.3 | 1977 | 19.3 | 1976 | 19.3 | 1975 | 19.3 | 1974 | 19.3 | 1973 | 19.3 | 1972 | 19.3 | 1971 | 19.3 | 1970 | 19.3 | 1969 | 19.3 | 1968 | 19.3 | 1967 | 19.3 | 1966 | 19.3 | 1965 | 19.3 | 1964 | 19.3 | 1963 | 19.3 | 1962 | 19.3 | 1961 | 19.3 |
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