Year	% of revenue
1972	11.029825548677547
1973	11.18421052631579
1974	8.620023192887514
1975	7.565162110616656
1976	8.168761220825854
1977	8.040071923966092
1978	8.104886769964244
1979	8.062205852261101
1980	6.865671641791045
1981	5.502116198537899
1982	5.389882924674176
1983	4.718792866941015
1984	4.558553838092743
1985	3.631129271916791
1986	3.054461627125156
1987	2.726500347570866
1988	2.7424942263279446
1989	2.4506683640993
1990	1.9975380483437781
1991	2.173803905818565
1992	1.934569923414051
1993	1.5981491368570921
1994	1.350519693654267
1995	1.220621920989049
1996	1.1941164065795022
1997	1.1232856104104505
1998	1.1654407956075832
1999	1.2645673196131912
2000	1.426992970825399
2001	1.554642228065249
2002	1.997150997150997
2003	0.05144344247412697
2004	0.0657210142943206
2005	0.06207485192561363
2006	0.06151516585435102
2007	0.04762358319839985