Year	% of revenue
1973	0.7204916295825387
1974	0.7069635913750442
1975	0.8552976086577063
1976	0.6283343212803794
1977	0.6923938499134508
1978	0.7930720145852324
1979	0.8259161254109535
1980	0.8226815338591242
1981	2.0874751491053676
1991	4.473829791030926
1992	4.740241411944412
1993	4.9025331646719215
1994	5.7474476488561
1995	4.877026922181706
1996	6.26369230183072
1997	6.613372093023257
1998	5.578858803513334
1999	6.432135947216482