Year	% of revenue
1997	12.783536127384707
1998	12.475726863946235
1999	9.846433414483785
2000	9.96937502880612
2001	8.782783730980997
2002	6.986959427098957
2003	5.9680277512865025
2004	4.663738060102576
2005	3.4423129840281743
2006	2.5883663703065705
2007	1.98050529897239
2008	1.9624712601053178
2009	2.2536082628847187
2010	2.6850224607266053
2011	3.252343364768013
2012	3.6164424232308283
2013	3.2310286371802945
2014	3.115983795641126
2015	4.480334929703263
2016	4.567914466334196
2017	4.398880860655799
2018	4.277480240776765
2019	4.062627066696803
2020	4.551925365378967
2021	4.72262559623045
2022	3.8319277469974384