Year	% of revenue
1972	27.239732569245508
1973	27.391808986901033
1974	18.63547120418842
1975	11.882669859323531
1976	14.12960609911057
1977	20.41791604197897
1978	20.183567205012828
1979	18.8534192414702
1980	18.97137591430054
1981	18.58576911721291
1982	18.75570006740948
1983	19.081272084805654
1984	19.01066643415589
1985	18.07828451238908
1986	16.552532833020717
1987	17.019475021168446
1988	17.22039719277289
1989	16.687227177832558
1990	15.60722131470741
1991	15.53211756422827
1992	14.088179790701632
1993	10.269212535681504
1994	8.516161739768894
1995	7.619972628140038
1996	7.0031735140235005
1997	5.586172344689379
1998	3.7358039450089664
1999	3.618618089566964
2000	3.5946531791907517
2001	3.5394156037587674
2002	3.395621435517359
2003	2.616326059346496
2004	0.9187744016296046
2005	0.02789244672542675
2006	0.025489829558006355
2007	0.00429553264604811
2008	0.01508233584248557
2009	0.010474964834046628
2010	0.017060964513193815
2011	0.02688628516443086
2012	0.02020260324973304
2013	0.03671296579575353
2014	0.0014487924315083377
2015	0.057296588296687025
2016	-0.018852858658958457
2017	0.06402397911431094
2018	0.05535819334476418
2019	0.16961473776764693
2021	0.158271178922444
2022	0.019895400834449285