Year	% of revenue
1972	4.110228865016348
1973	4.56968773800457
1974	4.549823774431272
1975	3.5755148741418767
1976	3.553892915595043
1977	3.203883495145631
1978	3.3640226628895182
1979	3.4588890517367727
1980	3.188921356879685
1981	3.6934441366574333
1982	3.4005712245626563
1983	4.0218597899410815
1984	4.785562942938555
1985	3.4752234918003673
1986	3.7037037037037033
1987	3.517417801519825
1988	2.027202312567172
2001	3.293938684764802
2002	2.9441243117942344
2003	2.975774938209899
2004	2.8457272076298734
2005	1.606099942538165
2006	1.6983173642365412
2007	2.7877738805630212
2008	2.8706592991129853
2009	2.798396863292526
2010	2.918864444100912
2011	2.7067891296915296
2012	2.865242928003653
2013	2.7663451345635584
2014	2.7808865439590296
2015	2.9144795913791146
2016	2.8292087968603785
2017	2.7809693725586433
2018	2.8502106345917326
2019	2.711516619268815
2020	2.994193980240572
2021	2.8120289067458315
2022	2.684618794083161