Year | Value | 2021 | 8.7370087468618 | 2020 | 7.1665296618853 | 2019 | 6.5967527828522 | 2018 | 6.5595130843333 | 2017 | 6.544621211248 | 2016 | 6.5849323052587 | 2015 | 6.6676046399039 | 2014 | 6.7830889787746 | 2013 | 6.9254257757178 | 2012 | 7.0571518248425 | 2011 | 7.199881146221 | 2010 | 7.3026323566676 | 2009 | 7.4530943454018 | 2008 | 7.5130848169712 | 2007 | 7.5970939914966 | 2006 | 7.6552624737471 | 2005 | 7.8169268584813 | 2004 | 7.9490977176346 | 2003 | 8.072707507288 | 2002 | 8.2381720065565 | 2001 | 8.4183945380635 | 2000 | 8.5701159748944 | 1999 | 8.700942424131 | 1998 | 8.967201475026 | 1997 | 9.2316047211554 | 1996 | 9.4882020755146 | 1995 | 9.6811758076621 | 1994 | 9.8812623673815 | 1993 | 10.104173937196 | 1992 | 10.317621569353 | 1991 | 10.694039139109 | 1990 | 10.826655044412 | 1989 | 11.143256076323 | 1988 | 11.398890678839 | 1987 | 11.696503249571 | 1986 | 11.971647192111 | 1985 | 12.316928347732 | 1984 | 12.607243254858 | 1983 | 12.867949461166 | 1982 | 13.198366590904 | 1981 | 13.493425331629 | 1980 | 13.804732432204 | 1979 | 14.102067971089 | 1978 | 14.383863194463 | 1977 | 14.705874457913 | 1976 | 15.022073732289 | 1975 | 15.355795832775 | 1974 | 15.782061431965 | 1973 | 16.133908061479 | 1972 | 16.461643744563 | 1971 | 19.155188474313 | 1970 | 17.471204473431 | 1969 | 17.323479392548 | 1968 | 17.603590324017 | 1967 | 18.703697294695 | 1966 | 19.006641841099 | 1965 | 19.455255638343 | 1964 | 18.797043061449 | 1963 | 19.113012877989 | 1962 | 19.389219210767 | 1961 | 19.722225263925 | 1960 | 20.012997647906 |
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