Year	% of revenue
1998	12.055709604234938
1999	11.826429252391058
2000	12.430881727436448
2001	12.986062986062985
2002	14.778496116631231
2003	14.899688689034937
2004	14.36534990976539
2005	12.931190830280388
2006	10.918336823212684
2007	9.909498821203133
2008	9.902776837878685
2009	12.447788368855091
2010	11.641732859022465
2011	10.206161251352793
2012	11.16462382689734
2013	11.00337599120672
2014	11.267282040540035
2015	11.568320513879025
2016	11.230688815041214
2017	10.562171324398996
2018	9.67702915205032
2019	11.192811681018346
2020	9.547851452933918
2021	9.425805626895677