Year	% of revenue
1972	19.901315789473685
1973	19.164265129683
1974	11.013215859030836
1977	1.2378721980595517
1978	0.6896551724137931
1979	0.631347790282734
1980	0.31810294968189706
1981	0.5995582202587567
1982	0.8426966292134831
1983	0.6031363088057901
1984	1.0555300596603947
1985	0.7643647865050079
1986	0.42158516020236086
1990	0.03209242618741977
1992	0.17094017094017094
1993	0.044111160123511246
1994	0.03929273084479371
1995	0.03348961821835231
1997	0.023872045834328
1998	0.028901734104046246