Year | Value | 2021 | 19.821 | 2020 | 20.326 | 2019 | 21.276 | 2018 | 21.137 | 2017 | 20.643 | 2016 | 20.25 | 2015 | 21.3 | 2014 | 22.057 | 2013 | 22.177 | 2012 | 22.353 | 2011 | 22.282 | 2010 | 22.274 | 2009 | 22.664 | 2008 | 24.08 | 2007 | 22.629 | 2006 | 22.455 | 2005 | 21.913 | 2004 | 21.261 | 2003 | 20.473 | 2002 | 20.04 | 2001 | 20.392 | 2000 | 20.705 | 1999 | 21.848 | 1998 | 22.41 | 1997 | 23.29 | 1996 | 25.214 | 1995 | 26.457 | 1994 | 27.065 | 1993 | 27.866 | 1992 | 28.723 | 1991 | 30.127 | 1990 | 31.146 | 1989 | 33.297 | 1988 | 34.899 | 1987 | 36.225 | 1986 | 36.482 | 1985 | 35.73 | 1984 | 35.231 | 1983 | 34.604 | 1982 | 34.366 | 1981 | 33.886 | 1980 | 34.29 | 1979 | 34.541 | 1978 | 34.776 | 1977 | 35.375 | 1976 | 36.175 | 1975 | 36.95 | 1974 | 37.58 | 1973 | 38.296 | 1972 | 38.744 | 1971 | 39.195 | 1970 | 39.376 | 1969 | 39.665 | 1968 | 39.778 | 1967 | 39.947 | 1966 | 39.972 | 1965 | 40.014 | 1964 | 40.072 | 1963 | 40.028 | 1962 | 39.963 | 1961 | 39.911 | 1960 | 39.52 |
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