Year	% of total
1970	19.082343930989378
1971	18.719040965030786
1972	20.47253083589344
1973	22.68165305097687
1974	19.829514699556704
1975	20.50661617060506
1976	17.2524360490478
1977	22.245960445547045
1978	16.861978402786757
1979	15.494477366455442
1980	16.472164102990455
1981	16.317537511484268
1982	17.97800909830782
1983	20.659008720335184
1984	18.769791019465185
1985	9.807565251709242
1986	7.388450226629413
1987	7.425687254773364
1988	9.023837129400068
1989	10.452871171798625