Year	% of revenue
1998	7.883806002277965
1999	8.17017827781824
2000	7.625456870561783
2003	11.035377830959222
2008	17.039944214792584
2009	13.566533701039301
2010	12.458297837762917
2011	18.00183203083249
2012	20.07504539912527
2013	12.982348294810139
2014	15.910805521865711
2015	16.392132163132338
2016	18.213743296015238
2017	7.278199237475063
2018	16.532358425894557
2019	15.20698215866795
2020	15.567846444845232
2021	15.576318456036942
2022	14.800831424163723