Year	% of revenue
1972	43.4009109916368
1973	45.80910315660226
1974	41.11377049667742
1975	43.006934111900286
1976	44.61945413009499
1977	48.80756354753934
1978	49.324931650499984
1979	50.199036760369566
1980	47.69912224268104
1981	47.141873278236915
1982	46.02092571311678
1983	44.7812604062604
1984	43.033445729613064
1985	41.9590497764578
1986	43.40766781733342
1987	42.64363637599079
1988	42.48505564751243
1989	41.291505204771674
1990	41.62736553041609
1991	41.085254431388165
1992	39.87327969480121
1993	38.15149791273329
1994	39.270149578391106
1995	38.47728746023522
1996	38.95686208176517
1997	39.86051965404875
1998	41.72930687876934
1999	41.55283310992653
2000	39.742283992933274
2001	40.74176422966745
2002	41.99522206244429
2003	41.58453732858934
2004	40.15585499518881
2005	39.27167755614073
2006	40.40866979578797
2007	38.82023931585726
2008	37.24395198420336
2009	37.40508684681728
2010	36.635375220277744
2011	36.15372790161414
2012	36.18584734191062
2013	35.742700573788596
2014	33.309715545630034
2015	35.97089207364758
2016	36.79017100411872
2017	36.021517953852666
2018	37.17487512918676
2019	33.94585011118457
2020	34.790728626091436
2021	32.11045712773917
2022	33.91125705438261