Year	% of revenue
1997	18.477148949792024
2002	9.893570582758773
2003	7.6451329866363
2004	7.875729684200044
2005	6.844740696073725
2006	6.087619667356195
2007	6.401343340188199
2008	6.195238013101115
2009	6.211160001745675