Year	% of total
1970	53.21163031382662
1971	51.50550823081158
1972	50.595158929007475
1973	49.832928941743134
1974	48.34788743926133
1975	47.572128468101354
1976	46.99010854216885
1977	47.207285327580124
1978	46.89471163752626
1979	46.739208126201156
1980	46.84247566824482
1981	46.70667222298475
1982	46.96666196548932
1983	45.09027340010554
1984	47.16115457163607
1985	46.88122500304574
1986	46.28402669662294
1987	45.70976318187333
1988	45.28619518760182
1989	44.63268776385926
1990	50.82478005865103
1991	48.50523168908819
1992	47.67333208746029
1993	46.37599093997735
1994	45.86310643098909
1995	44.835414301929625
1996	44.671286757819814
1997	43.954613095238095
1998	44.009000562535164
1999	44.27308632687606
2000	43.94502228826151
2001	40.578034682080926
2002	42.98076923076923
2003	42.162582652664334
2004	43.4341424592121
2005	42.279338513648135
2006	43.15082434357826
2007	43.09853420195439
2008	43.54348266774782