Year	% of revenue
1972	2.946273830155979
1973	2.3703703703703702
1974	2.8265107212475633
1975	5.992268041237113
1976	4.624027657735523
1977	3.71000680735194
1978	2.2526934378060726
1979	2.34375
1980	3.1314930246363906
1981	3.6559643777829858
1982	3.4936708860759493
1983	3.8798388509371167
1984	3.9645112301174965
1985	3.8797495996506037
1986	1.062273392277845
1987	2.99837925445705
1988	3.7680645447291425
1989	3.8193082895459183
1990	4.7012638835695135
1991	6.261822632691666
1992	7.310473524609284
1993	7.017438243734071
1994	7.546253662620344
1995	8.94132257063024
1996	9.336997264104326
1997	9.836896627727572
1998	9.004526738604302
1999	10.178250371300896
2000	8.16322865706886
2001	6.073380259124366
2002	5.712465091468592
2003	5.281382486591744
2004	5.58348035947638
2005	5.792188119883146
2006	6.452459722773507
2007	6.979355961621457
2008	6.963911758378635
2009	7.60457977662488
2010	6.629359406132572
2011	6.413450872277761
2012	3.1819225146768244
2013	3.6651486500950563
2014	3.0998674419250336
2015	2.968784296064338
2016	2.7641368545858978
2017	3.0304090683277614
2018	2.8259833004476076
2019	3.188091069804854
2020	3.6665222087647704
2021	4.799213489991815
2022	4.761499440166179