Year | Value | 2021 | 20 | 2020 | 16.9 | 2019 | 14.6 | 2018 | 14.6 | 2017 | 14.8 | 2016 | 14.3 | 2015 | 14.6 | 2014 | 14.2 | 2013 | 14 | 2012 | 14.2 | 2011 | 14.2 | 2010 | 14.2 | 2009 | 14.2 | 2008 | 13.97 | 2007 | 13.92 | 2006 | 13.88 | 2005 | 14.3 | 2004 | 14 | 2003 | 13.9 | 2002 | 13.7 | 2001 | 13.2 | 2000 | 13.8 | 1999 | 13.5 | 1998 | 13.13 | 1997 | 12.91 | 1996 | 12.9 | 1995 | 12.3 | 1994 | 10.891 | 1993 | 10.95 | 1992 | 10.922 | 1991 | 10.931 | 1990 | 10.988 | 1989 | 11.113 | 1988 | 11.069 | 1987 | 11.19 | 1986 | 11.063 | 1985 | 10.93 | 1984 | 11.03 | 1983 | 10.854 | 1982 | 10.341 | 1981 | 10.042 | 1980 | 9.773 | 1979 | 9.675 | 1978 | 9.393 | 1977 | 9.097 | 1976 | 9.035 | 1975 | 8.947 | 1974 | 8.814 | 1973 | 8.868 | 1972 | 8.863 | 1971 | 8.916 | 1970 | 8.994 | 1969 | 9.074 | 1968 | 8.887 | 1967 | 8.853 | 1966 | 8.503 | 1965 | 8.705 | 1964 | 8.722 | 1963 | 8.566 | 1962 | 8.668 | 1961 | 8.782 | 1960 | 8.828 |
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