Year | Value | 2021 | 1.6929062715059 | 2020 | 1.6762402760094 | 2019 | 1.6891235108136 | 2018 | 1.7155979469526 | 2017 | 1.7338590099689 | 2016 | 1.7805852230784 | 2015 | 1.7750089149812 | 2014 | 1.7673827539528 | 2013 | 1.735151690879 | 2012 | 1.7422351681663 | 2011 | 1.7128277828498 | 2010 | 1.7280467502064 | 2009 | 1.7218640871143 | 2008 | 1.7208981800585 | 2007 | 1.6614855010564 | 2006 | 1.6178838506118 | 2005 | 1.5864875282763 | 2004 | 1.591934697042 | 2003 | 1.5597161731092 | 2002 | 1.5483341002019 | 2001 | 1.5494931469646 | 2000 | 1.558477415305 | 1999 | 1.5484106674285 | 1998 | 1.5762315606427 | 1997 | 1.600283174288 | 1996 | 1.6292773986009 | 1995 | 1.6595482357445 | 1994 | 1.7041697381297 | 1993 | 1.7457223572549 | 1992 | 1.8218968009358 | 1991 | 1.8994184760854 | 1990 | 1.9625824602607 | 1989 | 2.0087392073937 | 1988 | 2.069368663844 | 1987 | 2.097907657969 | 1986 | 2.1068352534 | 1985 | 2.097809035074 | 1984 | 2.1126987711063 | 1983 | 2.1327863819685 | 1982 | 2.1416342113255 | 1981 | 2.1320886860492 | 1980 | 2.1672963254344 | 1979 | 2.1928557058217 | 1978 | 2.216493120752 | 1977 | 2.2509110550932 | 1976 | 2.3069947073847 | 1975 | 2.3442694443201 | 1974 | 2.3996085486593 | 1973 | 2.4135961478192 | 1972 | 2.4781224953638 | 1971 | 2.5403241175235 | 1970 | 2.555462074775 | 1969 | 2.6030019748799 | 1968 | 2.6533360032142 | 1967 | 2.7090695338894 | 1966 | 2.7086051768586 | 1965 | 2.7430749503151 | 1964 | 2.7872884935188 | 1963 | 2.796968184454 | 1962 | 2.8014518277373 | 1961 | 2.8236824957802 | 1960 | 2.8314289593664 |
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