Year	% of revenue
1999	34.280468311654246
2000	30.939052899595744
2001	35.013260743589406
2002	28.301477223029046
2003	31.25252292840556
2004	25.78886226960607
2005	23.62254213873006
2006	20.607954257956788
2007	23.975844622164193
2008	16.35485903180367
2009	22.48273694343218
2010	21.12281950296394
2011	19.52041984200095
2012	20.91804244972712
2013	21.08706644262052
2014	21.64348983662685
2015	19.417123427560647
2016	21.443554457874125
2017	22.264861595277875
2018	21.71425124064921
2019	22.156691767524126
2020	23.656434739992303
2021	25.329613174468594
2022	21.69562409832337