Year	% of total
1970	18.072774895825376
1971	16.167235873411407
1972	15.524955371454574
1973	14.898394000792695
1974	14.42276684672294
1975	14.256291402253185
1976	13.852019952071688
1977	13.522183106265844
1978	13.257194473803176
1979	12.953061406108207
1980	13.215942519540471
1981	13.208732839862295
1982	12.464070672774115
1983	11.810627516344654
1984	11.257354526623255
1985	10.433011279545036
1986	9.48656753311762
1987	9.245697664120454
1988	9.195777392847932
1989	9.221894083410408