Year	% of revenue
1972	2.5480387114872127
1973	1.9635545498399885
1974	1.7049180327868798
1975	1.6502231480267424
1976	1.6581713921631065
1977	1.9826699877004357
1978	1.968250308159612
1979	1.8856039341079724
1980	1.6300623685754294
1981	1.6170861937452323
1982	1.5276322506112243
1983	2.049622375789285
1984	1.76470588235294
1985	2.3918146062922814
1986	1.925144350955379
1987	2.432224992216442
1988	2.2283907262741547
1989	1.685345526087728
1990	1.905098212315162
1991	2.3136433539050785
1992	2.1313670814082313
1993	2.4041674750806523
1994	1.8977414568663007
1995	2.4607384841640845
1996	2.4402158842118347
1997	2.4891206743620824
1998	2.6085167660975106
1999	2.471346629964708
2000	2.051231263071429
2001	1.4590098743955469
2002	1.4072716451381726
2003	1.8446056006646117
2004	1.8446829322054912
2005	1.9780127316925904
2006	1.9748789346246975
2007	1.828494499067545
2008	1.903154773237766
2009	1.7197161266891712
2010	1.784377976891943
2011	2.339195092114058
2012	1.9575374769073621
2013	2.081549956602077
2014	2.052722136348741
2015	2.0369898501652255
2016	1.394390733779927
2017	1.902351866930536
2018	1.3582751550422394
2019	1.941766085353551
2020	1.8634599500575235
2021	1.6418022785692359
2022	1.582727380837945