Year	% of tax revenue
1973	0.8867213478164493
1974	0.30144694533762056
1975	0.15892636411795846
1976	0.015532774153463835
1977	0.013711778417660787
1978	0.012787723785166228
1979	0.012000480019200763
1980	0.01116944041103542