Year | Value | 2021 | 14.019 | 2020 | 14.235 | 2019 | 14.534 | 2018 | 14.805 | 2017 | 15.17 | 2016 | 15.496 | 2015 | 15.886 | 2014 | 16.396 | 2013 | 17.005 | 2012 | 17.318 | 2011 | 17.512 | 2010 | 17.553 | 2009 | 17.907 | 2008 | 18.468 | 2007 | 18.979 | 2006 | 19.203 | 2005 | 18.821 | 2004 | 18.771 | 2003 | 18.885 | 2002 | 18.914 | 2001 | 18.806 | 2000 | 18.189 | 1999 | 17.703 | 1998 | 17.458 | 1997 | 17.937 | 1996 | 18.39 | 1995 | 18.88 | 1994 | 19.289 | 1993 | 19.761 | 1992 | 20.36 | 1991 | 20.483 | 1990 | 20.586 | 1989 | 20.86 | 1988 | 20.828 | 1987 | 21.472 | 1986 | 22.076 | 1985 | 23.004 | 1984 | 23.768 | 1983 | 24.523 | 1982 | 25.945 | 1981 | 27.726 | 1980 | 28.146 | 1979 | 28.788 | 1978 | 28.465 | 1977 | 27.888 | 1976 | 27.96 | 1975 | 27.86 | 1974 | 27.923 | 1973 | 28.814 | 1972 | 29.313 | 1971 | 29.725 | 1970 | 30.631 | 1969 | 31.396 | 1968 | 32.292 | 1967 | 33.15 | 1966 | 33.114 | 1965 | 33.78 | 1964 | 34.432 | 1963 | 34.809 | 1962 | 35.113 | 1961 | 35.672 | 1960 | 36.56 |
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