Year | Value | 2021 | 16.093 | 2020 | 16.628 | 2019 | 17.215 | 2018 | 17.737 | 2017 | 18.399 | 2016 | 18.78 | 2015 | 19.119 | 2014 | 19.303 | 2013 | 19.33 | 2012 | 19.184 | 2011 | 18.934 | 2010 | 18.211 | 2009 | 17.667 | 2008 | 17.328 | 2007 | 17.085 | 2006 | 16.916 | 2005 | 16.883 | 2004 | 16.754 | 2003 | 16.68 | 2002 | 16.531 | 2001 | 16.686 | 2000 | 17.002 | 1999 | 17.305 | 1998 | 18.179 | 1997 | 19.126 | 1996 | 20.146 | 1995 | 21.3 | 1994 | 22.553 | 1993 | 23.626 | 1992 | 24.63 | 1991 | 25.552 | 1990 | 26.426 | 1989 | 26.991 | 1988 | 28.647 | 1987 | 30.168 | 1986 | 31.582 | 1985 | 32.316 | 1984 | 32.88 | 1983 | 33.267 | 1982 | 33.778 | 1981 | 34.289 | 1980 | 34.3 | 1979 | 35.266 | 1978 | 36.383 | 1977 | 37.87 | 1976 | 38.845 | 1975 | 39.221 | 1974 | 39.514 | 1973 | 39.842 | 1972 | 40.21 | 1971 | 40.857 | 1970 | 41.98 | 1969 | 43.142 | 1968 | 44.413 | 1967 | 45.592 | 1966 | 46.54 | 1965 | 47.084 | 1964 | 46.703 | 1963 | 46.843 | 1962 | 46.886 | 1961 | 46.816 | 1960 | 46.684 |
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