Year	% of total
1970	3.5488261105676204
1971	3.455870095558989
1972	3.670950771387603
1973	3.8951275152707097
1974	4.0203217307429
1975	4.217851880220034
1976	4.321292390077657
1977	4.8084365189672615
1978	4.620671710566509
1979	4.769944827414778
1980	4.540595875461224
1981	4.947253809581477
1982	5.750597715629387
1983	5.37415737522924
1984	5.699022004240608
1985	5.198142545100365
1986	4.838297648316039
1987	4.6835058626435435
1988	3.2296197257238335
1989	3.28257237183017
1990	5.22273425499232
1991	5.50314465408805
1992	6.335616438356165
1993	6.785714285714286
1994	6.190476190476191
1995	6.655290102389079
1996	6.018518518518518
1997	5.78386605783866
1998	5.637982195845697
1999	5.420827389443652
2000	5.382436260623229
2001	5.439330543933055
2002	5.347593582887701
2003	5.326231691078561
2004	5.263157894736842
2005	5.140758873929008
2006	5.134189031505251
2007	5.72851805728518
2008	5.896805896805897