Year	% of revenue
1972	28.05755395683449
1973	28.97862232779097
1974	29.07949790794969
1975	29.69396195202647
1976	30.141190914671522
1977	31.14330056906359
1978	31.648936170212817
1979	32.14809384164214
1980	32.788732394366285
1981	32.91167833747461
1982	30.64027108970924
1983	29.31246163290365
1984	30.787423483583748
1985	30.744167861331956
1986	33.60964581763391
1987	34.97039359108333
1988	37.27714748784436
1989	34.380716668460046
1990	35.38804859905784
1991	35.84525877519519
1992	36.517626827171036
1993	37.718455374322566
1994	39.137432657155564
1995	36.60593869210666
1996	37.87460800353213
1997	38.707532212938105
1998	39.131737091692635
1999	40.6646527523456
2000	40.67787680011962
2001	40.011890611168845
2002	39.484863071763236
2003	40.25848215848548
2004	40.269412125770856
2005	38.62664320277201
2006	39.38866542891898
2007	38.738953150601866
2008	37.07323781661373
2009	36.51482061982039
2010	35.929601670553886
2011	35.47091456146441
2012	36.73018929481594
2013	36.36093257960797
2014	36.230400902269686
2015	38.956654413477494
2016	39.35528581476498
2017	40.02939457852409
2018	41.62163944341356
2019	41.865284593449395
2020	45.00945973324946
2021	46.51789403204655
2022	49.67084529576211