Year	% of revenue
1972	15.842598010532452
1973	16.398752399232237
1974	17.355290405285515
1975	18.14356042559947
1976	20.09751536200907
1977	18.847337050567205
1978	20.855273055513752
1979	21.914064953828717
1980	23.115865109822845
1981	22.926038794562913
1982	19.30273980827343
1983	21.74253915770454
1984	22.551955712859588
1985	24.327465743694393
1986	22.37398408443099
1987	27.94152386836514
1988	28.03122772812548
1989	31.80715015890012
1990	31.66012465275767
1991	31.759894641990705
1992	31.165029665715377
1993	29.986821551596883
1994	29.302188634802267
2012	16.077314706357875
2013	19.870155485797003
2014	20.33294280054435
2015	19.989170250039816
2016	19.68084938302814
2017	19.720669029955292
2018	20.657187544433388
2019	19.33690775796039
2020	17.95994849200529
2021	20.409175922745142
2022	22.500917683249522