Year	% of revenue
1972	2.0348837209302237
1973	1.8181818140495891
1974	1.7006802721088419
1975	2.443991853360484
1976	2.4432809773123925
1977	2.168674698795178
1978	2.30769230769231
1979	1.1807817589576546
1980	1.6129032258064515
1981	1.3717188823031352
1982	1.447863009884453
1988	0.6210777643194308
1989	1.1571225947571708