Year	% of revenue
1972	33.09352517985615
1973	33.72921615201907
1974	31.694560669456003
1975	30.603804797353185
1976	31.123388581952067
1977	31.19503362648728
1978	35.10638297872338
1979	32.038123167155554
1980	30.056338028168895
1981	29.274903998192908
1982	30.10522561084361
1983	31.87538367096377
1984	31.95603784084584
1985	30.939658542942716
1986	37.75433308214033
1987	35.8295599674911
1988	37.763371150729256
1989	40.966318734531285
1990	37.92710141334001
1991	35.27541107158952
1992	35.19346517626823
1993	32.949912789008316
1994	35.389205179085515
1995	35.821794817047056
1996	36.15757275182276
1997	35.79614581952254
1998	36.18972866932933
1999	35.84608974346906
2000	38.1291324908637
2001	37.10071399302764
2002	38.216431556609564
2003	38.26886063856362
2004	38.52398698517993
2005	39.08521269066755
2006	38.73279372917228
2007	37.83036081748293
2008	35.90110364311132
2009	33.07135935057758
2010	32.73744069060883
2011	30.337062389443016
2012	29.98720444521254
2013	30.88686720430473
2014	31.55019485917337
2015	31.121992311646522
2016	31.305358016187903
2017	31.503564695337527
2018	30.180055818643353
2019	30.231766931126646
2020	27.994866689456327
2021	28.574149611028147
2022	26.26367047116618