Year	% of revenue
1972	4.38683011601146
1973	1.9061203319502076
1974	1.4477977161500815
1975	0.9619472789115646
1976	1.0126869053013139
1977	2.622290466029872
1978	3.7362957037144784
1979	5.2498212231446075
1980	4.887438586199311
1981	4.854127198917456
1982	4.12574588309766
1983	2.030609094517708
1984	1.7413447829705875
1985	1.116960198040473
1986	1.140687124797453
1987	0.9460775810304106
1988	0.8403512344717706
1989	0.8739208023171132
1990	5.999377842297836
1991	6.811047761986254
1992	6.666909044636933
1993	6.66900971299204
1994	5.888575161195162
1995	5.318124754503654
1996	5.419047030288043
1997	5.570905704434881
1998	5.2799572320319506
1999	5.262673549781365
2000	5.318726855933697
2001	5.98265302585515
2002	5.763587057468703
2003	5.411465200260148
2004	5.16599520628283
2005	4.983239700971608
2006	5.11766295898106
2007	5.109549226215126
2008	8.994660736989765
2009	5.885640869948106
2010	5.085109356666222
2011	5.662655364592504
2012	5.701249524722256
2013	5.989117055775505
2014	5.764988119323177
2015	5.91157906672042
2016	5.793296172870869
2017	5.897503968007411
2018	5.977327378907591
2019	5.881582919472859
2020	4.654875086647543
2021	4.640158009518976
2022	4.637109895306812