Year	% of revenue
1972	2.701863354037267
1973	2.4285714285714284
1974	1.1491836591689442
1975	1.5982296533071059
1976	1.7935327319723586
1977	2.343928131697752
1978	6.914219919401267
1979	4.6110643077787135
1980	7.384615384615385
1981	7.947984395318596
1982	7.256420709335508
1983	7.462088315852762
1984	8.802864025695932
1985	9.51850727131626
1986	14.287130676184812
1987	12.348677922905384
1988	13.881777108433734
1989	10.35248041775457
1990	8.133595284872298
1991	9.293724648055356
1992	8.699902248289346
1993	6.5891472868217065
1994	5.340527268027914
1995	6.494142799875284
1996	5.738992437614367
1997	6.252845874766821
1998	10.829700027760088
1999	11.605780089256262
2000	11.483915249649327
2001	16.623333379141
2002	12.04989797647185
2003	13.431207658791516
2004	12.956468034985589
2005	10.44122120338577
2006	12.418446771827451
2007	12.571042902593451
2008	14.911452473229888
2009	18.68831069153427