Year	% of revenue
1972	16.546762589928075
1973	15.914489311163878
1974	15.271966527196579
1975	13.813068651778313
1976	14.241866175567806
1977	12.002069322296933
1978	7.579787234042561
1979	7.441348973607037
1980	8.84507042253522
1981	10.865145696860164
1982	9.34546103085429
1983	7.151626764886436
1984	6.997774067890923
1985	6.998566401668183