Year	% of revenue
1972	29.72084237039106
1973	30.22588522588524
1974	30.61052187219669
1975	32.46386685483476
1976	32.730480811645336
1977	33.41465334067833
1978	34.688459018654534
1979	34.18617824773414
1980	34.66770419044318
1981	34.62584322543537
1982	35.17871066730399
1983	35.3917249305621
1984	35.29115696872864
1985	36.53700747710664
1986	36.763493818474274
1987	36.80061973467605
1988	36.18934783779413
1989	36.80530563981277
1990	36.554040074483105
1991	36.372587922343214
1992	36.46917534027227
1993	37.45899958999599
1994	38.76718186816541
1995	35.01332136721682
1996	34.37401915524115
1997	34.06479782422317
1998	33.88604911533661
1999	33.65234367693648
2000	33.410207999829815
2001	32.01587236034659
2002	32.30452326521805
2003	32.66731773244423
2004	32.719662139589204
2005	32.224904716463215
2006	32.31353861716013
2007	31.68922429991976
2008	31.522197898278044
2009	32.38844247471293
2010	32.42895860411558
2011	32.30286620672748
2012	32.11669346939718
2013	32.381106030639
2014	32.55648271515327
2015	32.197771953697604
2016	33.07079332012942
2017	33.55786676153178
2018	33.65902600601587
2019	33.7349923775527
2020	35.617052650909024
2021	34.07660631459245
2022	32.96055077697271