Year	% of revenue
1972	0.6627605417347017
1973	0.5366135556839754
1974	0.4993086495621464
1975	0.45422909264075506
1976	0.43675346590345104
1977	0.40696085279557787
1978	0.2525539160045406
1979	0.06885228536624079
1980	0.01879301839366701