Year	% of total
1970	55.015895497599324
1971	60.99462461238495
1972	62.805887286070416
1973	64.44046973529609
1974	68.1489956644213
1975	70.88843216453685
1976	69.4725388993486
1977	66.26118967776236
1978	63.569564491255
1979	67.08088720419228
1980	67.9015358259267
1981	64.95018160401422
1982	57.95358623000172
1983	55.514539271708685
1984	45.102743651064806
1985	47.4856291295101
1986	48.30787362590723
1987	45.86639463269233
1988	52.45397526028825
1989	55.1584668373425
1990	77.03703703703704
1991	76.29629629629629
1992	74.21875
1993	74.04580152671755
1994	72.22222222222221
1995	73.68421052631578
1996	71.53846153846153
1997	69.23076923076923
1998	69.50354609929079
1999	70.66666666666667
2000	65.69343065693431
2001	64.44444444444444
2002	65.06849315068493
2003	65.1006711409396
2004	66.0493827160494
2005	66.66666666666666
2006	68.15642458100558
2007	68.44919786096256
2008	67.72486772486772