Year	% of tax revenue
1973	0.006038282712396595
1974	0.028653295128939826
1975	0.05279831045406547
1976	0.09087958455047063
1977	0.1904545325336138
1978	0.30407668917177755
1979	0.09470322651690342
1985	0.01356682181544948
1986	0.069631648579017
1987	0.04640327285124436
1988	0.005950508768499707
1990	0.024210958148668735
1991	0.0006211141545704685
1993	0.0006148359924990009