Year	% of revenue
1996	11.67414436400602
1997	8.650130778478157
1998	8.246499592953397
1999	6.676860340718855
2000	5.977522484037145
2002	7.006122975183107
2003	6.929985092062603
2004	6.956157023800916
2005	6.145049915029766
2006	5.302446160070129
2007	5.2823585654659135
2008	5.07959696356699
2009	4.11427762128818
2010	4.026889860019997
2011	4.162687461186694
2012	4.361769670577791
2013	4.1249883008171295
2014	3.370364630339721
2015	3.397196295192657
2016	3.317253019084673
2017	3.135465305240119
2018	3.0416642788468717
2019	3.0410514417241155
2020	2.994021573624401
2021	3.265553902901971
2022	2.9200196021149654