Year	% of revenue
1972	35.9803921568627
1973	44.59107483938179
1974	49.294354838709694
1975	53.39029466535234
1976	52.27738222959116
1977	42.35462345090573
1978	41.87455168566182
1980	23.841664908950275
1981	32.45868691380081
1982	35.050903802202306
1983	38.733856672575264
1984	40.6824282469544
1985	37.4663620208175
1986	33.331577006164714
1987	31.042704249231797
1988	35.73198871891288
1989	30.975007326160704
1990	34.66736147298929
1991	35.53492762743864
1992	26.09048686219102
1993	23.87841109483807
1994	26.500629634811773