Year	% of revenue
1972	5.090769378541903
1973	5.068934202922472
1974	4.8970656014749006
1975	4.9342466757024
1976	4.906859014657713
1977	4.434051082698087
1978	4.744608399545985
1979	4.77993750331021
1980	4.484484014188734
1981	4.870108298451927
1982	6.535811668713455
1983	6.430379746835444
1984	7.901328273244795
1985	8.161460870820491
1986	7.754470725222023
1987	6.591696964572595
1988	5.552171980708131
1989	6.162167089530699
1990	0.37072948154907936
1991	5.218450865021516
1992	6.882473599943142
1993	6.829693091607562
1994	6.917113151109554
1995	5.216517845525564
1996	4.645869133260097
1997	4.476079008081599
1998	4.280493709252737
1999	4.305859322693158
2000	4.192007427365199
2001	4.823772695703161
2002	4.608788853161844
2003	5.76685413180303
2004	4.42506810300211
2005	3.9332632321176466
2006	4.237130284864497
2007	4.164526640626686
2008	4.375873471556192
2009	4.675915679007298
2010	4.836852525285995
2011	5.502356593458716
2012	5.2170469168544615
2013	5.216649776305707
2014	5.658229248579256
2015	5.341083406886917
2016	5.297616995436847
2017	4.835529254606329
2018	5.286256975042696
2019	5.505572292845421
2020	5.748784780253636
2021	5.702558253401594
2022	5.449370454028679