Year	% of revenue
1972	2.399063779988295
1973	2.699136276391554
1974	2.1398284192880412
1975	1.850087343179289
1976	1.6898209991985043
1977	1.7736973658911783
1978	1.921919663005869
1979	2.076135435642938
1980	1.0124928553931596
1981	1.0061432786726616
1982	1.6570936818300062
1983	4.519966594515358
1984	6.927428381280808
1985	10.924565096666711
1986	11.440772254776263
1987	9.792662317602806
1988	9.738594752234349
1989	9.002023629877396
1990	9.653176582812875
1991	10.633996441856667
1992	11.023348941335945
1993	13.508164023344706
1994	14.67317695554033
2012	8.043606655822193
2013	10.176613946584562
2014	10.055512223458727
2015	8.942188246536073
2016	8.408828780433856
2017	7.830829952856047
2018	7.395137210294327
2019	6.829248276616698
2020	6.443696333808763
2021	5.940175833683219
2022	6.435042663826166