Year | Value | 2021 | 14.948 | 2020 | 15.332 | 2019 | 15.822 | 2018 | 16.311 | 2017 | 16.904 | 2016 | 17.395 | 2015 | 17.764 | 2014 | 17.89 | 2013 | 17.872 | 2012 | 17.899 | 2011 | 17.866 | 2010 | 17.565 | 2009 | 17.205 | 2008 | 17.143 | 2007 | 17.34 | 2006 | 17.694 | 2005 | 18.034 | 2004 | 18.571 | 2003 | 19.169 | 2002 | 19.712 | 2001 | 20.161 | 2000 | 20.499 | 1999 | 20.96 | 1998 | 21.425 | 1997 | 21.974 | 1996 | 22.667 | 1995 | 23.12 | 1994 | 23.93 | 1993 | 24.881 | 1992 | 25.915 | 1991 | 26.911 | 1990 | 27.844 | 1989 | 28.63 | 1988 | 28.66 | 1987 | 28.836 | 1986 | 29.258 | 1985 | 29.756 | 1984 | 30.447 | 1983 | 30.816 | 1982 | 31.152 | 1981 | 31.474 | 1980 | 31.421 | 1979 | 31.413 | 1978 | 31.524 | 1977 | 31.7 | 1976 | 31.807 | 1975 | 31.924 | 1974 | 32.19 | 1973 | 32.437 | 1972 | 32.756 | 1971 | 32.954 | 1970 | 33.318 | 1969 | 33.678 | 1968 | 34.11 | 1967 | 34.657 | 1966 | 35.243 | 1965 | 35.897 | 1964 | 36.667 | 1963 | 37.374 | 1962 | 37.865 | 1961 | 38.349 | 1960 | 38.836 |
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