Year | Value | 2021 | 17.828 | 2020 | 18.302 | 2019 | 18.732 | 2018 | 19.282 | 2017 | 19.898 | 2016 | 20.576 | 2015 | 21.214 | 2014 | 21.908 | 2013 | 21.886 | 2012 | 21.953 | 2011 | 23.885 | 2010 | 23.562 | 2009 | 23.126 | 2008 | 23.391 | 2007 | 23.623 | 2006 | 23.771 | 2005 | 23.648 | 2004 | 23.338 | 2003 | 23.052 | 2002 | 22.811 | 2001 | 22.611 | 2000 | 21.195 | 1999 | 21.649 | 1998 | 22.188 | 1997 | 22.813 | 1996 | 23.478 | 1995 | 24.148 | 1994 | 24.944 | 1993 | 25.933 | 1992 | 27.111 | 1991 | 28.253 | 1990 | 29.479 | 1989 | 30.695 | 1988 | 31.851 | 1987 | 32.852 | 1986 | 33.681 | 1985 | 34.357 | 1984 | 34.792 | 1983 | 35.551 | 1982 | 36.338 | 1981 | 37.128 | 1980 | 38.545 | 1979 | 40.142 | 1978 | 40.698 | 1977 | 41.254 | 1976 | 41.89 | 1975 | 42.581 | 1974 | 43.349 | 1973 | 43.392 | 1972 | 44.263 | 1971 | 45.479 | 1970 | 46.404 | 1969 | 47.503 | 1968 | 48.643 | 1967 | 49.918 | 1966 | 51.194 | 1965 | 51.922 | 1964 | 51.962 | 1963 | 51.691 | 1962 | 51.125 | 1961 | 50.733 | 1960 | 50.463 |
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