Year	% of revenue
1981	16.122840690978887
1982	14.634146341463413
1983	11.929824561403509
1984	12.182361733931241
1985	15.31464637089289
1986	11.651285431773237
1987	10.00908540278619
1988	11.748322572477528
1989	14.500758068009532
1990	15.53485848630075
1991	15.420408163265305
1992	13.457109959700633
1993	13.625648279113625
1994	16.11298889425398
1995	9.16156232795813
1996	11.903019129580242
1997	9.9012631614155
1998	8.737229717431868
1999	7.96870703285639
2000	7.639081842364728
2001	8.020312482794289
2002	7.189214987896793
2003	7.223156713503929
2004	8.999717907157986
2005	8.893568856526468
2006	10.392382110993257
2007	9.296801228170368
2008	9.446522218742999
2009	11.546931481409528
2010	12.707539031899708
2011	12.203684060927102
2012	13.422532636443849
2013	14.722907149994802
2014	14.617950806199667
2015	15.830859138903994
2016	11.344295303155661
2017	12.85638864675781
2018	13.832324391211706
2019	14.888595963225487
2020	15.238773496645585
2021	15.533499340656398
2022	15.531319673721969