Year	% of revenue
1972	1.7737617135207495
1973	1.6592920353982303
1974	1.7529013539651837
1975	2.179501937761406
1976	2.012522361359571
1977	2.7030675260689097
1978	2.506424696214981
1979	2.4820155087041824
1980	2.547568099011046
1981	2.7927976641072783
1982	2.560075780237312
1983	2.381348480167312
1984	2.1462047216503874
1990	3.3462419798138576
1991	3.5635535040211797
1992	4.29299398497683
1993	4.169432312633097
1994	5.017082474391729
1995	4.7743044253337175
1996	4.2665123137206615
1997	4.44306851322517
1998	4.515961191012426
1999	4.782055101492767
2000	4.192489807493975
2001	4.155446535243757
2002	4.0900762005252576
2003	3.6206423921743838
2004	3.651958646052763
2005	3.985622032056769
2006	4.259091793333707
2007	3.7545253386768507
2008	3.26001086886333
2009	2.92004728391258
2010	2.6945165638301174
2011	2.409453755573674
2012	2.170226735060462
2013	1.8811367255048732
2014	1.7547393330073002
2015	1.6194258348475383
2016	1.4302613017115917
2017	1.157878641823285
2018	0.9427168527759335
2019	0.8433535092539622
2020	0.7526767191213184
2021	0.5902223580377688
2022	0.6765678346938304