Year	% of revenue
1972	10.22530329289428
1973	12.148148148148149
1974	12.378167641325536
1975	13.015463917525775
1976	14.866032843560934
1977	16.167460857726347
1978	18.97649363369246
1979	16.982886904761905
1980	15.048975957257346
1981	13.932505273025544
1982	13.336708860759494
1983	15.755824137327027
1984	15.354488050515547
1985	14.194205852380259
1986	14.941797595572801
1987	17.31496488384657
1988	14.043798209061087
1989	10.869735707003372
1990	11.761138771862631
1991	9.163235785022811
1992	7.296477723349662
1993	5.787329681134991
1994	5.781498534951863
1995	6.538059891055855
1996	6.398621204999337
1997	6.389684813753583
1998	4.023088042822526
1999	4.421714651546842
2000	4.307345656007102
2001	4.175398483654564
2002	4.246718334126961
2003	4.070555819749113
2004	3.8781686360169836
2005	3.3507899499107903
2006	3.3279601250362716
2007	3.140070708128632
2008	3.5585513662131163
2009	3.735231616090483
2010	4.013205341527146
2011	3.8239397917707625
2012	2.495062718919017
2013	2.7621190729820233
2014	2.187618447466798
2015	2.047897185909959
2016	1.798942021434763
2017	1.7772974391993257
2018	1.5843102432196527
2019	1.4186024511387267
2020	1.2972991848429318
2021	1.3769641896468958
2022	1.400790696876526