Year	% of revenue
1997	3.819298980589303
1998	6.659808721559342
1999	10.080125036484668
2000	9.96937502880612
2001	8.13498666238417
2002	6.986959427098957
2003	4.902816606240037
2004	3.570374789823333
2010	1.7269837882206627
2011	1.6174553872869177
2012	1.6199233392397636
2013	2.057291625696891
2014	2.564994489579213
2015	4.480334929703263
2016	7.840604420795283
2017	4.5504681449233395
2018	5.728042994216246
2019	6.28036306653355
2020	10.18893462382553
2021	8.892017182465274