Year	% of total
1970	38.36772533105686
1971	37.52718193970093
1972	36.99977440619942
1973	35.855326170728155
1974	35.685925745662374
1975	35.390116580701864
1976	35.315993286976244
1977	34.969790667492276
1978	35.483969696597555
1979	35.58635248762942
1980	39.504386700362176
1981	42.76568964094975
1982	43.59784217369224
1983	44.111502232552226
1984	44.32319594752956
1985	45.697353480017604
1986	43.804780909242744
1987	44.762272169618186
1988	44.9550490749236
1989	45.329865166460884
1990	60.89743589743589
1991	61.875
1992	62.42424242424243
1993	64.07185628742515
1994	67.27272727272727
1995	67.05882352941175
1996	67.06586826347305
1997	66.46706586826348
1998	68.55345911949685
1999	65.77181208053692
2000	62.857142857142854
2001	61.31386861313869
2002	60.60606060606061
2003	58.46153846153847
2004	55.81395348837209
2005	53.125
2006	50.74626865671642
2007	50
2008	47.91666666666667