Year | Value | 2022 | 19.05 | 2021 | 18.94 | 2020 | 18.841 | 2019 | 18.754 | 2018 | 18.678 | 2017 | 18.612 | 2016 | 18.558 | 2015 | 18.515 | 2014 | 18.482 | 2013 | 18.461 | 2012 | 18.45 | 2011 | 18.45 | 2010 | 18.45 | 2009 | 19.213 | 2008 | 20.131 | 2007 | 21.084 | 2006 | 22.068 | 2005 | 23.085 | 2004 | 24.133 | 2003 | 25.216 | 2002 | 26.329 | 2001 | 27.473 | 2000 | 27.774 | 1999 | 27.971 | 1998 | 28.168 | 1997 | 28.366 | 1996 | 28.565 | 1995 | 28.765 | 1994 | 28.965 | 1993 | 29.167 | 1992 | 29.369 | 1991 | 29.572 | 1990 | 29.349 | 1989 | 29.061 | 1988 | 28.774 | 1987 | 28.488 | 1986 | 28.205 | 1985 | 27.923 | 1984 | 27.643 | 1983 | 27.364 | 1982 | 27.087 | 1981 | 26.812 | 1980 | 26.54 | 1979 | 26.268 | 1978 | 25.998 | 1977 | 25.73 | 1976 | 25.465 | 1975 | 25.2 | 1974 | 24.938 | 1973 | 24.677 | 1972 | 24.419 | 1971 | 24.162 | 1970 | 23.907 | 1969 | 23.654 | 1968 | 23.403 | 1967 | 23.153 | 1966 | 22.905 | 1965 | 22.66 | 1964 | 22.416 | 1963 | 22.174 | 1962 | 21.934 | 1961 | 21.696 | 1960 | 21.46 |
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