Year | Value | 2021 | 11.1 | 2020 | 12.5 | 2019 | 14.1 | 2018 | 14 | 2017 | 14.6 | 2016 | 16.3 | 2015 | 17.2 | 2014 | 17.9 | 2013 | 18.3 | 2012 | 18.8 | 2011 | 19.2 | 2010 | 18.3 | 2009 | 17 | 2008 | 17.4 | 2007 | 17.7 | 2006 | 17.6 | 2005 | 16.9 | 2004 | 15.8 | 2003 | 13.8 | 2002 | 13.5 | 2001 | 13.6 | 2000 | 14.5 | 1999 | 14.7 | 1998 | 15.7 | 1997 | 16.8 | 1996 | 16.6 | 1995 | 18.9 | 1994 | 21.4 | 1993 | 23.7 | 1992 | 25.2 | 1991 | 26.6 | 1990 | 25.9 | 1989 | 26.4 | 1988 | 26.4 | 1987 | 26.8 | 1986 | 27.6 | 1985 | 26.6 | 1984 | 26.6 | 1983 | 26.1 | 1982 | 25.2 | 1981 | 26.3 | 1980 | 27.671 | 1979 | 27.061 | 1978 | 26.765 | 1977 | 26.745 | 1976 | 27.02 | 1975 | 27.426 | 1974 | 27.859 | 1973 | 28.199 | 1972 | 29.081 | 1971 | 30.183 | 1970 | 31.317 | 1969 | 32.647 | 1968 | 34.304 | 1967 | 36.124 | 1966 | 38.926 | 1965 | 41.037 | 1964 | 43.387 | 1963 | 45.35 | 1962 | 46.637 | 1961 | 47.587 | 1960 | 47.791 |
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