Year	% of revenue
1997	5.711903529740342
1998	8.76425975437558
1999	26.292969522356863
2000	24.431222748501206
2001	31.296175920590798
2002	16.50833480188232
2003	13.846599250182779
2004	14.56788711961821
2010	27.55948929635681
2011	22.892130624285873
2012	39.2862802062956
2013	20.671977399635715
2014	25.46687336382849
2015	25.97685373414388
2016	26.18502746982505
2017	34.81016179597733
2018	25.84376007505474
2019	23.999826662521645
2020	21.41454034915998
2021	27.80852342029091