Year	% of revenue
1997	3.626331940629954
2002	2.6940759173450934
2003	2.727061442477165
2004	2.8788675680700706
2005	3.988315244147833
2006	3.5443039366395457
2007	2.838129465796648
2008	2.2291923684407835
2009	2.609819373640736