Year	% of revenue
1997	3.626331940629954
2002	2.6940759173450934
2003	2.727061442477165
2004	2.8788675680700706
2005	3.535989576045367
2006	2.919359092707372
2007	2.686348858717481
2008	2.113463406480504
2009	2.419497191942181