Year | Value | 2021 | 16.376 | 2020 | 16.363 | 2019 | 16.624 | 2018 | 17.02 | 2017 | 17.997 | 2016 | 19.123 | 2015 | 19.15 | 2014 | 19.615 | 2013 | 19.469 | 2012 | 21.422 | 2011 | 20.088 | 2010 | 21.169 | 2009 | 21.335 | 2008 | 21.682 | 2007 | 21.927 | 2006 | 21.47 | 2005 | 20.404 | 2004 | 21.751 | 2003 | 21.092 | 2002 | 20.85 | 2001 | 23.146 | 2000 | 23.89 | 1999 | 24.203 | 1998 | 24.523 | 1997 | 24.631 | 1996 | 24.811 | 1995 | 24.976 | 1994 | 25.236 | 1993 | 25.511 | 1992 | 25.857 | 1991 | 26.225 | 1990 | 26.543 | 1989 | 26.815 | 1988 | 27.084 | 1987 | 27.627 | 1986 | 28.078 | 1985 | 27.654 | 1984 | 26.93 | 1983 | 28.323 | 1982 | 27.274 | 1981 | 28.186 | 1980 | 29.212 | 1979 | 29.19 | 1978 | 29.458 | 1977 | 31.317 | 1976 | 32.336 | 1975 | 32.04 | 1974 | 31.56 | 1973 | 31.266 | 1972 | 31.609 | 1971 | 32.07 | 1970 | 32.48 | 1969 | 32.586 | 1968 | 30.949 | 1967 | 31.39 | 1966 | 32.904 | 1965 | 31.671 | 1964 | 32.08 | 1963 | 32.442 | 1962 | 33.927 | 1961 | 33.606 | 1960 | 33.021 |
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