Year	% of revenue
1997	45.523337964893386
1998	43.70021641202836
1999	27.999295115189245
2000	25.556141528430338
2001	20.106577773604396
2002	11.059531325435437
2003	7.691685407801706
2004	7.5653900547119415
2005	7.019124599290566
2006	5.927711970872222
2007	6.681266528693879
2008	6.9348782697100955
2009	6.468351707000523
2010	6.939599616070204
2011	5.899927830744104
2012	6.016395548268645
2013	6.239708388418069
2014	5.293866528642617
2015	5.351486780005802
2016	4.997193744409509
2017	4.5095958436980315
2018	4.566244792512732
2019	3.9838819588838814
2020	2.361508056749952
2021	2.5201135235349525