Year	% of total
1970	4.480740157999344
1971	4.474056096545078
1972	4.4354159377595685
1973	4.335888428925816
1974	4.507404295508693
1975	4.488946605608883
1976	4.249740553742784
1977	4.527579540606426
1978	4.518016885090373
1979	4.6058472399115455
1980	6.811452495876903
1981	12.432043521420091
1982	8.468226476822508
1983	8.54760562257798
1984	7.260667625308134
1985	7.7294973054546245
1986	6.8434290991134485
1987	6.640923864186432
1988	7.909640540620588
1989	7.27499104691417