Year	% of revenue
1972	11.51079136690648
1973	9.976247030878877
1974	10.774058577405837
1975	10.835401157981828
1976	10.374462860650699
1977	11.588204862907377
1978	12.234042553191502
1979	15.029325513196456
1980	14.98591549295775
1981	13.869437542353738
1982	15.65899768146959
1983	16.436464088397766
1984	14.426822481914336
1985	15.678352665189612
1986	13.58955036423011
1987	14.443283408800694
1988	9.659643435980527
1989	9.04982244700311
1990	10.934787999008206
1991	13.070651924155143
1992	12.458297506448822
1993	12.621846612145518
1994	9.347819552164752