Year	% of revenue
1972	32.83500654735923
1973	32.715008431703204
1974	31.694560669456003
1975	30.157130522815315
1976	29.64467890191238
1977	28.39517267281498
1978	27.553927954121498
1979	27.344072538733677
1980	29.05467917967487
1981	27.862516914749662
1982	28.831896876248315
1983	29.589624894375255
1984	29.964007518341937
1985	30.051103434493392
1986	29.614370468029005
1987	29.680076121057663
1988	30.28420957050758
1989	30.189958994764766
1990	31.191715090525797
1991	31.2021001778904
1992	31.556134564791513
1993	31.965042326915757
1994	32.250274651244744
1995	31.401916553002486
1996	32.64868004823933
1997	32.357172692254146
1998	31.279747931905256
1999	32.75383715021961
2000	31.660140399724014
2001	31.08825877396175
2002	32.21526313764869
2003	31.32101954577354
2004	32.28131561854446
2005	32.01929188002304
2006	32.153276010023504
2007	32.23017224190555
2008	30.980055761322237
2009	29.99970143202426
2010	30.63865955175733
2011	30.963453431372674
2012	30.89468130486518
2013	30.563306286848402
2014	30.41915192492266
2015	30.323963255254505
2016	30.29350145290104
2017	30.384788689620056
2018	29.382778327094307
2019	30.231766931126646
2020	29.49092228858494
2021	30.297123531491295
2022	27.866955102733904