Year	% of revenue
1972	59.35761372668193
1973	57.173895220136096
1974	56.782652546646496
1975	55.920172821726155
1976	55.63878351443451
1977	57.011661414990165
1978	57.8606236646902
1979	58.03896688633293
1980	56.55821792335311
1981	54.202160083777486
1982	52.670517426964416
1983	49.911222678013836
1984	49.49465419311727
1985	50.04738138859056
1986	50.0941596705019
1987	52.39717746367414
1988	51.49235899726773
1989	52.48865319382734
1990	51.63498028812498
1991	48.81693541433129
1992	49.92385171852826
1993	50.69119583747405
1994	51.38712465707091
1995	52.093700776425656
1996	54.151225792958314
1997	55.25666352429732
1998	56.6080888572319
1999	55.85881117963522
2000	57.46233276125277
2001	55.281422291406216
2002	50.84920476686827
2003	50.118423553149704
2004	50.785190063616234
2005	54.24192589032756
2006	55.754391529102044
2007	56.00746671558796
2008	53.318742392538844
2009	45.491292732085995
2010	47.65666859793091
2011	52.78367589784219
2012	53.53475127267468
2013	51.17376738813704
2014	53.09640716486235
2015	54.19752460946741
2016	54.018975183199835
2017	49.582671112407226
2018	51.64235117810612
2019	52.02415098796141
2020	52.842350124718806
2021	55.66164867623568
2022	57.72492256000675