Year | Value | 2017 | 3.6794941056813 | 2016 | 3.4120750835077 | 2015 | 3.3007397068333 | 2014 | 2.9920282564218 | 2013 | 2.8172005313113 | 2012 | 2.5201463048786 | 2011 | 2.2794907623243 | 2010 | 2.1388148564033 | 2009 | 2.0354177466631 | 2008 | 2.1076050810158 | 2007 | 1.9344827602995 | 2006 | 1.8700611163636 | 2005 | 1.8765782960503 | 2004 | 1.8417153967375 | 2003 | 1.7305298995898 | 2002 | 1.4914387253481 | 2001 | 1.6580987830951 | 2000 | 1.7080797759298 | 1999 | 2.5048498678264 | 1998 | 2.2532982606705 | 1997 | 2.498755906422 | 1996 | 2.5409773918012 | 1995 | 2.5722218259156 | 1994 | 2.3484849587749 | 1993 | 2.2914885341465 | 1992 | 2.2775196252356 | 1991 | 2.2721144684452 | 1990 | 2.2781955693859 | 1989 | 2.3543627418762 | 1988 | 2.5367118692888 | 1987 | 2.4799694124507 | 1986 | 2.3657315614909 | 1985 | 2.1194219280196 | 1984 | 2.3081555033094 | 1983 | 2.2620676936283 | 1982 | 2.2337271255722 | 1981 | 2.2940862151301 | 1980 | 2.2224557656535 | 1979 | 2.2000000476837 | 1978 | 2.1400001049042 | 1977 | 2.0699999332428 | 1976 | 1.9870312293876 | 1975 | 1.7797586427231 | 1974 | 1.8500000238419 | 1973 | 1.7699999809265 | 1972 | 1.710000038147 | 1971 | 1.5800000429153 | 1970 | 1.4394710201403 | 1969 | 1.4500000476837 | 1968 | 1.4500000476837 | 1967 | 1.5 | 1966 | 1.5199999809265 | 1965 | 1.4400000572205 |
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