Year	% of total
1970	8.38158641237763
1971	8.79224540890324
1972	8.991867922823634
1973	9.594314782784656
1974	9.418878218574745
1975	9.746045908290004
1976	10.13153493464513
1977	10.622344536296438
1978	10.455109547518276
1979	10.879659721108556
1980	11.572747861223252
1981	12.360906644490631
1982	13.327002164188077
1983	14.053294350415808
1984	14.590284774732854
1985	15.351023167357697
1986	16.04718924780274
1987	16.602665636333143
1988	17.093063528750076
1989	17.50972826695566
1990	9.922480620155039
1991	10.56782334384858
1992	10.72
1993	10.801963993453354
1994	10.726072607260726
1995	10.666666666666668
1996	10.738255033557047
1997	10.416666666666668
1998	10.211267605633804
1999	10.09009009009009
2000	9.48905109489051
2001	9.22242314647378
2002	8.75912408759124
2003	8.582089552238806
2004	8.31758034026465
2005	7.9245283018867925
2006	7.547169811320755
2007	7.238095238095238
2008	6.994328922495274