Year	% of total
1970	1.5525843739943086
1971	1.5289790261916392
1972	1.5018049677946892
1973	1.6333423243804466
1974	1.7144300187594108
1975	1.5916329290535467
1976	1.4847455661360862
1977	1.1980959727772498
1978	1.3854165028270855
1979	1.3930024018536378
1980	1.855527460319329
1981	2.226896657187547
1982	2.5998083179485656
1983	3.1303019756392434
1984	3.1107162206861947
1985	3.3023483814110506
1986	3.6375021839016024
1987	3.641947518151563
1988	3.9843055542136687
1989	3.793011706183569