Year | Value | 2021 | 18.5 | 2020 | 15.9 | 2019 | 14.7 | 2018 | 14.8 | 2017 | 14.5 | 2016 | 14.7 | 2015 | 14.9 | 2014 | 14.7 | 2013 | 14.6 | 2012 | 14.5 | 2011 | 14.5 | 2010 | 15.2 | 2009 | 15.3 | 2008 | 16.3 | 2007 | 16.4 | 2006 | 16.2 | 2005 | 16.6 | 2004 | 16 | 2003 | 16 | 2002 | 15.7 | 2001 | 15.3 | 2000 | 15.4 | 1999 | 14.9 | 1998 | 14.4 | 1997 | 14.9 | 1996 | 15.2 | 1995 | 15.4 | 1994 | 14.7 | 1993 | 14.2 | 1992 | 13.4 | 1991 | 12.9 | 1990 | 12.1 | 1989 | 11.6 | 1988 | 11.6 | 1987 | 11.4 | 1986 | 11.1 | 1985 | 12.135 | 1984 | 12 | 1983 | 11.5 | 1982 | 11.3 | 1981 | 11.3 | 1980 | 11.369 | 1979 | 11.11 | 1978 | 10.661 | 1977 | 10.441 | 1976 | 10.15 | 1975 | 9.988 | 1974 | 9.938 | 1973 | 9.736 | 1972 | 9.682 | 1971 | 9.409 | 1970 | 9.402 | 1969 | 9.116 | 1968 | 8.634 | 1967 | 8.453 | 1966 | 8.217 | 1965 | 7.979 | 1964 | 7.624 | 1963 | 7.732 | 1962 | 7.892 | 1961 | 7.602 | 1960 | 7.512 |
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