Year	% of revenue
1975	3.1347962382445194
1976	4.552590266875977
1978	9.889604415823309
1979	10.6715063520871
1980	10.143388210302678
1981	16.324804398392924
1982	17.1467299220603
1983	18.17729083665336
1984	21.337411665436203
1985	23.266083643605466
1986	25.07496251874067
1987	23.259752497878743
1988	21.51718667028706
1989	17.797322867755256
1990	20.438194898626534
2010	8.69796467520842
2011	11.945964388788001
2012	13.134076354503021
2013	12.349869736172067
2014	12.619824780190953
2015	11.938542305365674
2016	11.018300722322376
2017	10.113677495789954
2018	8.88833445491217
2019	7.9070342227355495
2020	7.584847212875939
2021	6.12895075525459
2022	5.050606786099329