Year	% of revenue
1972	11.11111111111111
1973	8.641975308641975
1974	10.612244897959183
1975	9.900990099009901
1976	9.315068493150685
1977	9.79498861047836
1978	10.26086956521739
1979	6.012658227848101
1980	5.9620596205962055
1981	5.397448478900883
1982	4.403992953611274
1983	4.838135894699396
1984	10.22539857064321
1985	9.461107047061693
1986	15.432551319648095
1987	13.31335616438356
1988	14.443684450524398
1989	14.270613107822411
1990	13.63711681855841
1991	12.915333497415702
1992	11.246780925317468
1993	11.515347799489007
1994	9.564977467120391
1995	12.262517547964435
1996	9.586619256669513
1997	8.776933859243082
1998	9.248719023348249
1999	9.43860037648101
2000	8.958165454704323
2001	8.482013013453884
2002	8.530712315572872
2003	8.439913891351148
2004	8.274671473988228
2005	8.49829677216479
2006	11.042369175621255
2007	8.553055348165636
2008	6.978171261362936
2009	10.399038695633505
2010	8.051738993431048
2011	7.768466218062092
2012	8.492643726216093
2013	7.624842175735629
2014	7.487701155218325
2015	10.872423943737948
2016	11.365750491744695
2017	7.21184717328103
2018	14.622378977807784
2019	13.984283942885408
2020	14.392504954576982
2021	12.452961190647246
2022	14.433682431725078