Year	% of revenue
1972	4.754521963824289
1973	3.4676007005253937
1974	3.5628310062590276
1975	4.109825591434985
1976	3.029508196721311
1977	3.840389659048333
1978	4.293370616334615
1979	4.481760718909451
1980	4.233515945998826
1981	2.7222079627980014
1982	2.3470819434507493
1983	4.58490069859709
1984	4.73385301610678
1985	4.722886628307221
1986	4.447697439466296
1987	3.478191413078798
1988	2.84608844822116
1989	2.754042628951359
1990	3.075444273829868
1991	7.134132847974996
1992	7.98668051717696
1993	8.116953299249657
1994	8.070806362001697
1995	8.136708909486757
1996	8.735565354049301
1997	9.322239758903113
1998	8.925939907286267
1999	8.53329377294035
2000	8.799058250143087
2001	9.058952814561943
2002	9.228544408998957
2003	9.697171272727893
2004	9.222239279913412
2005	7.977784118709624
2006	7.979424048268485
2007	7.458498825315435
2008	6.496174735749764
2009	8.157295668059188
2010	11.800927563204036
2011	11.337447953581485
2012	10.222492535227438
2013	10.471495571040307
2014	9.937105494627998
2015	10.59051672764551
2016	7.054324912176783
2017	9.98529294523042
2018	10.396577025431661
2019	10.505649468376168
2020	10.176912068555822
2021	10.232041236638205
2022	9.49204778672591