Year | Value | 2021 | 8.3423558961849 | 2020 | 7.4430708194972 | 2019 | 7.213998301197 | 2018 | 7.3184167123387 | 2017 | 7.3464246359757 | 2016 | 7.5430925902434 | 2015 | 7.8053198786187 | 2014 | 8.0684971594966 | 2013 | 8.3034075432787 | 2012 | 8.5831909081975 | 2011 | 8.8387167049903 | 2010 | 9.0974615981996 | 2009 | 9.4940142452938 | 2008 | 9.7919786895331 | 2007 | 10.128177333941 | 2006 | 10.521698841122 | 2005 | 10.809264651586 | 2004 | 10.941877072288 | 2003 | 11.041371258951 | 2002 | 11.03505596451 | 2001 | 10.965263295142 | 2000 | 10.8906572446 | 1999 | 11.145618234377 | 1998 | 10.933436108193 | 1997 | 10.720596587208 | 1996 | 10.542615638066 | 1995 | 10.540988681455 | 1994 | 10.565159839966 | 1993 | 10.473355536275 | 1992 | 10.464985067144 | 1991 | 10.484020222591 | 1990 | 10.510402448029 | 1989 | 10.572896849233 | 1988 | 11.077383372252 | 1987 | 11.218792978577 | 1986 | 11.461143135545 | 1985 | 11.774949167437 | 1984 | 11.990591538687 | 1983 | 12.307197157275 | 1982 | 12.481824850061 | 1981 | 12.84062657034 | 1980 | 13.088042782948 | 1979 | 13.756397557667 | 1978 | 14.078271104653 | 1977 | 14.046157368559 | 1976 | 14.410148058425 | 1975 | 14.51619404962 | 1974 | 14.129845373266 | 1973 | 13.950523529528 | 1972 | 14.226900571762 | 1971 | 14.652012665016 | 1970 | 15.176219378794 | 1969 | 15.46139179118 | 1968 | 15.263860256404 | 1967 | 15.427439963822 | 1966 | 15.720287497606 | 1965 | 15.981259507472 | 1964 | 16.329600644308 | 1963 | 16.773587516802 | 1962 | 16.795770208006 | 1961 | 17.077934394717 | 1960 | 17.484067974369 |
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