Year	% of revenue
1972	3.8510854666843604
1973	3.7878512486822564
1974	3.208992166797702
1975	2.8814482454547843
1976	3.052036552941428
1977	2.8165390020386636
1978	2.8715463954254847
1979	3.0665772319969626
1980	2.9861770602511366
1981	3.097056825586066
1982	3.311208327047832
1983	3.5019325972113027
1984	3.5339409014439336
1985	3.49617086048611
1986	3.484263441643604
1987	3.7414995832053726
1988	4.5032751091703185
1989	4.6568197755960705
1990	6.645421314087514
1991	5.981764681002769
1992	5.621072799008493
1993	6.509401810719108
1994	7.683818647226641
1995	1.9356630761681421
1996	2.2711093999714764
1997	2.1469291166159103
1998	2.173265848979236
1999	2.517585806655155
2000	2.0993187297468565
2001	2.055562653201314
2002	2.272230875870187
2003	2.12765175242251
2004	1.770855269351386
2005	1.8973275042693403
2006	1.6932736671946054
2007	1.8026355365116025
2008	1.7377006451361123
2009	2.045492707926547
2010	1.853196632954172
2011	1.9757816957043177
2012	2.076315099141584
2013	2.0152906322763267
2014	1.9299603919110033
2015	2.396123799066176
2016	2.9130418028710325
2017	2.955010849616153
2018	3.255314406415725
2019	3.5703655103755434
2020	3.5018701505102
2021	3.2906598002978327
2022	3.384089860778651