Year | Value | 2021 | 13.083 | 2020 | 12.997 | 2019 | 12.989 | 2018 | 13.239 | 2017 | 13.435 | 2016 | 13.638 | 2015 | 13.803 | 2014 | 13.892 | 2013 | 14.004 | 2012 | 14.193 | 2011 | 14.336 | 2010 | 14.628 | 2009 | 14.82 | 2008 | 15.161 | 2007 | 15.322 | 2006 | 15.561 | 2005 | 15.883 | 2004 | 16.271 | 2003 | 16.541 | 2002 | 16.919 | 2001 | 17.158 | 2000 | 17.464 | 1999 | 17.865 | 1998 | 18.289 | 1997 | 18.531 | 1996 | 18.757 | 1995 | 18.859 | 1994 | 18.87 | 1993 | 18.702 | 1992 | 18.805 | 1991 | 18.819 | 1990 | 18.631 | 1989 | 18.58 | 1988 | 18.694 | 1987 | 18.807 | 1986 | 18.928 | 1985 | 18.795 | 1984 | 18.739 | 1983 | 18.759 | 1982 | 18.896 | 1981 | 18.982 | 1980 | 19.17 | 1979 | 19.343 | 1978 | 19.539 | 1977 | 19.886 | 1976 | 20.49 | 1975 | 21.269 | 1974 | 21.906 | 1973 | 22.485 | 1972 | 23.071 | 1971 | 23.708 | 1970 | 24.347 | 1969 | 25.152 | 1968 | 25.356 | 1967 | 26.201 | 1966 | 25.111 | 1965 | 25.207 | 1964 | 25.42 | 1963 | 25.594 | 1962 | 25.92 | 1961 | 25.999 | 1960 | 26.235 |
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