Year | Value | 2022 | 31.077 | 2021 | 31.012 | 2020 | 30.963 | 2019 | 30.931 | 2018 | 30.914 | 2017 | 30.914 | 2016 | 30.93 | 2015 | 30.962 | 2014 | 30.995 | 2013 | 31.027 | 2012 | 31.059 | 2011 | 31.091 | 2010 | 31.054 | 2009 | 30.992 | 2008 | 30.929 | 2007 | 30.867 | 2006 | 30.805 | 2005 | 30.743 | 2004 | 30.681 | 2003 | 30.619 | 2002 | 30.557 | 2001 | 30.495 | 2000 | 30.465 | 1999 | 30.449 | 1998 | 30.432 | 1997 | 30.416 | 1996 | 30.4 | 1995 | 30.522 | 1994 | 30.706 | 1993 | 30.891 | 1992 | 31.076 | 1991 | 31.262 | 1990 | 31.392 | 1989 | 31.497 | 1988 | 31.602 | 1987 | 31.707 | 1986 | 31.813 | 1985 | 31.832 | 1984 | 31.851 | 1983 | 31.871 | 1982 | 31.89 | 1981 | 31.909 | 1980 | 32.209 | 1979 | 32.599 | 1978 | 32.992 | 1977 | 33.387 | 1976 | 33.783 | 1975 | 34.183 | 1974 | 34.585 | 1973 | 34.989 | 1972 | 35.394 | 1971 | 35.803 | 1970 | 36.088 | 1969 | 36.346 | 1968 | 36.604 | 1967 | 36.864 | 1966 | 37.124 | 1965 | 37.385 | 1964 | 37.646 | 1963 | 37.909 | 1962 | 38.172 | 1961 | 38.436 | 1960 | 38.7 |
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