Year	% of total
1970	0.021053352786129402
1971	0.021422960266286883
1972	0.022634730538922156
1973	0.02224772554501091
1974	0.018101725815789796
1975	0.016731527561448162
1976	0.01657824273463015
1977	0.015861007384978684
1978	0.012351962249079158
1979	0.05081679242981372
1980	0.022292625838037983
1981	0.02412501280206127
1982	0.0624913950606718
1983	0.056352450351661046
1984	0.04570697164809003
1985	0.03683108843023275
1986	0.028820985673388852
1987	0.02195483978700113
1988	0.015984945054281174
1989	0.013139213008760503