Year	% of revenue
1996	13.204348802853815
1997	11.49917789708426
1998	13.215036497892523
1999	11.062955743117325
2003	13.353610675039246
2005	13.227044582226158
2006	13.608307470290102
2007	12.05003863686168
2008	14.103367889373574
2009	15.267080553028974
2010	15.061127359261747
2011	14.762828712085344
2012	14.116488972774102
2013	14.818959109470285
2014	15.641988311022425
2015	16.66438811543052
2016	17.507237150389653
2017	17.580914235294383
2018	18.522754585089235
2019	18.392630741282513
2020	16.79673313653999
2021	16.460240014286715
2022	15.391949824315427