Year	% of revenue
1988	28.322589073529002
1989	24.97397691099162
1990	24.86700336264182
1991	27.064471158888697
1992	30.84389427274988
1993	35.99351495775422
1994	35.2125228356263
1995	37.24012774577899
1996	36.5283148225191
1997	36.82858837903821
1998	38.38617147250656
1999	36.4493963445711
2000	36.199748363282346
2001	38.10839339569732
2002	38.25855303052924
2003	38.02919260752111
2004	37.9023673578177
2005	37.61760651214941
2006	39.17072221363614
2007	36.60746746046454
2008	36.599406223175166
2009	36.97318407565948
2010	42.33854747061994
2011	43.091281375504664
2012	45.04046084116287
2013	43.908714068193014
2014	46.12424242034949
2015	47.30014953186139
2016	48.70543777835036
2017	49.29346477163353
2018	47.79951752253781
2019	48.239194940502415
2020	45.81187114057624