Year	% of revenue
1972	6.552795031055901
1973	5.122448979591836
1974	2.319388970639759
1975	2.747725596262601
1976	2.6955741942290445
1977	2.9048292215787317
1978	4.001151410477835
1979	2.8194327436113453
1980	4.027972027972028
1981	3.833550065019506
1982	4.525071341214839
1983	4.95691094929521
1984	6.04590471092077
1985	8.75594695819415
1986	12.368629783858815
1987	10.636349155782096
1988	9.480421686746988
1989	6.360313315926892
1990	5.414840562188303
1991	6.418515867334765
1992	5.653307266210493
1993	2.7633378932968538
1994	3.660506590850349
1995	6.03091176339584
1996	5.977037552831441
1997	9.493103802823107
1998	12.18014663857999
1999	16.84901680248185
2000	7.5027043457802645
2001	5.570178129935342
2002	4.267076728610327
2003	4.360201645580743
2004	3.3284813477693276
2005	3.02422556252489
2006	2.668407753417143
2007	2.6368914010343847
2008	2.300166790116638
2009	3.515321590298565