Year | Value | 2014 | 16.77549802171 | 2013 | 18.759323531667 | 2012 | 22.164301887136 | 2011 | 22.991810815104 | 2010 | 21.570872042603 | 2009 | 18.761085374987 | 2008 | 26.861077111847 | 2007 | 30.286037441484 | 2006 | 30.022435568502 | 2005 | 27.687505989995 | 2004 | 26.682378743137 | 2003 | 25.705999892335 | 2002 | 23.363785999555 | 2001 | 24.608240525158 | 2000 | 21.81482697352 | 1999 | 22.907542678707 | 1998 | 29.208800624679 | 1997 | 29.596202599756 | 1996 | 30.897318035426 | 1995 | 30.289174940248 | 1994 | 26.060430882091 | 1993 | 26.573297081079 | 1992 | 26.288315922234 | 1991 | 29.92870102631 | 1990 | 34.408635727496 | 1989 | 28.046742974449 | 1988 | 23.496932280287 | 1987 | 24.355097550843 | 1986 | 18.994258471634 | 1985 | 16.358589834325 | 1984 | 13.982865760107 | 1983 | 14.332656683652 | 1982 | 14.8488106595 | 1981 | 15.517737243327 | 1980 | 19.379500452779 | 1979 | 18.550156796923 | 1978 | 15.751936296465 | 1977 | 9.1502964857318 | 1976 | 6.8135333145018 | 1975 | 3.5511326425961 | 1974 | 1.1091309774664 |
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