Year | Value | 2021 | 18.419 | 2020 | 18.791 | 2019 | 19.298 | 2018 | 19.816 | 2017 | 20.282 | 2016 | 20.803 | 2015 | 21.316 | 2014 | 21.342 | 2013 | 21.561 | 2012 | 21.943 | 2011 | 22.627 | 2010 | 23.421 | 2009 | 22.278 | 2008 | 21.135 | 2007 | 20.539 | 2006 | 20.712 | 2005 | 21.383 | 2004 | 22.221 | 2003 | 22.726 | 2002 | 23.29 | 2001 | 24.033 | 2000 | 24.787 | 1999 | 25.777 | 1998 | 26.289 | 1997 | 26.836 | 1996 | 27.49 | 1995 | 28.157 | 1994 | 29.266 | 1993 | 30.861 | 1992 | 32.604 | 1991 | 34.59 | 1990 | 36.588 | 1989 | 38.801 | 1988 | 41.261 | 1987 | 43.779 | 1986 | 46.502 | 1985 | 49.338 | 1984 | 50.686 | 1983 | 51.933 | 1982 | 52.807 | 1981 | 53.234 | 1980 | 53.353 | 1979 | 53.239 | 1978 | 53.025 | 1977 | 52.796 | 1976 | 52.246 | 1975 | 51.577 | 1974 | 50.529 | 1973 | 50.137 | 1972 | 49.884 | 1971 | 49.81 | 1970 | 49.935 | 1969 | 50.229 | 1968 | 50.626 | 1967 | 51.032 | 1966 | 51.502 | 1965 | 51.962 | 1964 | 52.419 | 1963 | 52.796 | 1962 | 53.141 | 1961 | 53.455 | 1960 | 53.687 |
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