Year	% of revenue
1990	16.51167566298991
1991	11.64741132292716
1992	13.72379713299786
1993	14.577756063274835
1994	12.221437515335747
1995	9.91579468763544
1996	8.382829105500486
1997	9.112690289141701
1998	8.49703246042154
1999	6.759451599501453
2000	5.567471198834379
2001	7.897041782571493
2002	6.716709333101923
2003	6.2602601480152495
2004	6.534682100907931
2005	6.561717871522362
2006	5.973676338618008
2007	5.211740312835633
2008	5.1461764086836315
2009	4.604640375083328
2010	4.630355890089674
2011	4.399771436881252
2012	4.371998801063361
2013	4.528812524522695
2014	4.029449354418939
2015	4.041802638225611
2016	4.294756244105814
2017	4.364288713411046
2018	4.405779161294973
2019	4.355930622308093
2020	3.432292582584754
2021	3.839009239591343
2022	4.289094931322756