Year	% of revenue
1990	17.643902338348504
1995	18.73985060084443
1996	14.625314861460959
1997	7.848509266720387
1998	11.131086142322097
1999	11.8583544115459
2009	38.25443786982248
2010	37.028196062243126
2011	35.063133701302796
2012	23.512192322607557
2013	19.315304211649615
2014	24.16000894831461
2015	49.88322760926225
2016	51.73457569760272
2017	49.910167000009245
2018	53.61567295007868
2019	57.91967371205929
2020	62.743030266245846
2021	63.64515620494572