Year | Value | 2021 | 8.7238710117417 | 2020 | 8.7238710117417 | 2019 | 8.7238710117417 | 2018 | 8.7238710117417 | 2017 | 8.7238710117417 | 2016 | 8.7238710117417 | 2015 | 8.7238710117417 | 2014 | 8.7238710117417 | 2013 | 8.7267126635371 | 2012 | 8.7267126635371 | 2011 | 8.7244393421008 | 2010 | 8.7244393421008 | 2009 | 8.7437625743092 | 2008 | 8.7437625743092 | 2007 | 8.7437625743092 | 2006 | 8.7437625743092 | 2005 | 8.7437625743092 | 2004 | 8.7437625743092 | 2003 | 8.7807040476488 | 2002 | 8.7807040476488 | 2001 | 8.7807040476488 | 2000 | 8.7807040476488 | 1999 | 8.7807040476488 | 1998 | 8.7807040476488 | 1997 | 8.9034634052082 | 1996 | 8.9034634052082 | 1995 | 8.8176455209884 | 1994 | 8.7949123066256 | 1993 | 8.7892290030349 | 1992 | 8.7892290030349 | 1991 | 8.7863873512395 | 1990 | 8.7835456994442 | 1989 | 8.7778623958535 | 1988 | 8.7750207440581 | 1987 | 8.7750207440581 | 1986 | 8.7721790922627 | 1985 | 8.7676324493902 | 1984 | 8.7608124850813 | 1983 | 8.7551291814906 | 1982 | 8.6909078509156 | 1981 | 8.630096502495 | 1980 | 8.5704218147925 | 1979 | 8.4539140911829 | 1978 | 8.3391113586506 | 1977 | 8.2208986439638 | 1976 | 8.103254259636 | 1975 | 7.9878831967446 | 1974 | 7.8702388124169 | 1973 | 7.7548677495254 | 1972 | 7.6372233651977 | 1971 | 7.5218523023063 | 1970 | 7.4025029269013 | 1969 | 7.2859952032918 | 1968 | 7.1694874796822 | 1967 | 7.0501381042773 | 1966 | 6.9353353717449 | 1965 | 6.8171226570581 | 1964 | 6.7023199245257 | 1963 | 6.5841072098389 | 1962 | 6.4693044773066 | 1961 | 6.3482501108244 |
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