Year	% of revenue
1972	34.07613741875585
1973	36.7407030426406
1974	40.860778661075756
1975	37.16056747153561
1976	36.66689009540398
1977	39.522593670209496
1978	41.095890410958994
1979	38.606539050272524
1980	35.657757879980174
1981	34.90358088530905
1982	35.04676421783083
1983	37.33290509784813
1984	36.75855876312067
1985	38.048803691195296
1986	36.79240128223788
1987	36.22866669591542
1988	35.76733492126513
1989	34.349433146329936
1990	34.091426429039984
1991	30.349298804251205
1992	27.115479328242344
1993	30.425612834076603
1994	32.79451966975151
1995	30.05312414451128
1996	30.565071899489453
1997	30.89860531371411
1998	29.852996322318702
1999	28.446456630286317
2000	28.376712519009818
2001	28.455155636308966
2002	28.741591086477815
2003	28.610745438837366
2004	26.31248187829253
2005	28.060457661582895
2006	28.216667368559197
2007	27.91035633822719
2008	28.835355735897572
2009	28.346044896963956
2010	29.344303394952693
2011	28.627109226461666
2012	28.837395788000673
2013	29.20307847956534
2014	28.783626394497226
2015	29.995472826445063
2016	30.27254948283456
2017	30.80870788414338
2018	33.0653022354584
2019	32.552266173446135
2020	31.972555902810022
2021	32.47727478838537
2022	32.79063989162964