Year | Value | 2022 | 29.864 | 2021 | 29.613 | 2020 | 29.38 | 2019 | 29.164 | 2018 | 28.965 | 2017 | 28.784 | 2016 | 28.619 | 2015 | 28.47 | 2014 | 28.338 | 2013 | 28.223 | 2012 | 28.123 | 2011 | 28.04 | 2010 | 27.973 | 2009 | 27.921 | 2008 | 27.886 | 2007 | 27.867 | 2006 | 27.863 | 2005 | 27.875 | 2004 | 27.903 | 2003 | 27.947 | 2002 | 27.992 | 2001 | 28.036 | 2000 | 28.08 | 1999 | 28.124 | 1998 | 28.168 | 1997 | 28.213 | 1996 | 28.257 | 1995 | 28.301 | 1994 | 28.346 | 1993 | 28.39 | 1992 | 28.435 | 1991 | 28.366 | 1990 | 27.869 | 1989 | 27.378 | 1988 | 26.893 | 1987 | 26.413 | 1986 | 25.938 | 1985 | 25.469 | 1984 | 25.006 | 1983 | 24.548 | 1982 | 24.095 | 1981 | 23.649 | 1980 | 23.215 | 1979 | 22.81 | 1978 | 22.41 | 1977 | 22.014 | 1976 | 21.625 | 1975 | 21.239 | 1974 | 20.859 | 1973 | 20.484 | 1972 | 20.115 | 1971 | 19.75 | 1970 | 19.39 | 1969 | 19.035 | 1968 | 18.685 | 1967 | 18.34 | 1966 | 18 | 1965 | 16.978 | 1964 | 16.004 | 1963 | 15.074 | 1962 | 14.189 | 1961 | 13.348 | 1960 | 12.551 |
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