Year	% of tax revenue
1972	1.6393442622950802
1973	0.8687424737656975
1974	0.4722061138265273
1975	0.065979381443299
1976	0.07513148009015784
1977	0.06835737234260723
1978	0.05766643172935228
1979	0.05367686527106818
1980	0.04503997297601625
1981	0.043972956631671556
1982	0.05417998591320375
1983	0.04690675978527134
1984	0.03804089396100801
1985	0.027285129604365722
1986	0.026573364630851706
1987	0.021248565721813786