Year	% of revenue
1972	0.429495760821062
1973	0.35951327433628316
1974	0.4754996776273372
1975	0.34150646559993864
1976	0.44034677308380354
1977	0.3914554719400668
1978	0.3363050858212507
1979	0.289620379309271
1980	0.266034353131687
1981	0.24332215853790418
1982	0.40632166716522083
1983	0.4301637474154526
1984	0.38982085760588675
2016	0.062357271840800275
2017	0.059608737860687405
2018	0.05964113390294222
2019	0.05455553029619786
2020	0.054694344025338154
2021	0.05003457866905827
2022	0.04982126129127919