Year | Value | 2015 | 19.478152630606 | 2014 | 17.084552590758 | 2013 | 16.414094439466 | 2012 | 16.458999458658 | 2011 | 11.98194306709 | 2010 | 8.1444255692176 | 2009 | 12.67197070511 | 2008 | 13.913424222117 | 2007 | 17.58464164524 | 2006 | 21.721673315952 | 2005 | 24.026251657519 | 2004 | 23.580332601789 | 2003 | 21.201504920273 | 2002 | 14.554768214941 | 2001 | 16.129103738271 | 2000 | 16.378600028437 | 1999 | 16.153758435149 | 1998 | 15.823022809276 | 1997 | 10.170491299574 | 1996 | 11.162091233144 | 1995 | 15.026055973923 | 1994 | 14.042114668117 | 1993 | 9.1633078242391 | 1992 | 8.4344784121274 | 1991 | 7.9041753845789 | 1990 | 10.183479104535 | 1989 | 9.6734883859467 | 1988 | 12.114385516399 | 1987 | 14.408996123516 | 1986 | 12.15946474566 | 1985 | 20.066862152383 | 1984 | 23.887720729669 | 1983 | 27.421639961664 | 1982 | 29.719686296664 | 1981 | 35.202427149581 | 1980 | 39.106481385641 | 1979 | 40.096682716149 | 1978 | 36.979242621569 | 1977 | 38.259300008896 | 1976 | 42.617045566813 | 1975 | 46.286132934639 | 1974 | 50.107675860437 | 1973 | 50.376189359279 | 1972 | 50.749120983835 | 1971 | 51.189982914771 | 1970 | 52.224483790031 | 1969 | 51.018454228079 | 1968 | 49.928494874773 | 1967 | 48.040142765614 | 1966 | 45.657781992852 | 1965 | 44.183417108884 | 1964 | 42.275633204041 | 1963 | 40.048171473038 | 1962 | 40.953223580297 | 1961 | 42.082919260482 | 1960 | 40.522185009678 |
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