Year	% of revenue
1972	14.285714285714285
1973	12.5
1974	7.003891050583658
1975	8.427876823338735
1976	7.364438839848677
1977	7.618085941882644
1978	6.25121587445691
1979	4.456681060095868
1980	4.159116884564993
1981	5.25901316598991
1982	3.5623133315232147
1983	6.9107775498788
1984	9.751704618551397
1985	10.896903070116636
1986	8.848008924567715
1987	10.399951054940828
1988	8.663604964512087
1989	10.309355900329102
1990	11.691109628127185
1991	10.321187463340095
1992	9.642582529136824
1993	9.938819159250626
1994	8.935622800024147
1995	9.343030802082316
1996	9.319268869528424
1997	8.394983625064423
1998	7.950781494277778
1999	6.926878991437933
2000	6.249095790913824
2001	5.39020458353317
2002	4.4669120091998336
2003	2.998125876134015
2004	2.025749106355919
2005	1.8162189623420335
2006	1.5652260605154278
2007	1.276551031399196
2008	1.3544927616639377
2009	0.8868038037015545
2010	1.1268448789165557
2011	1.0636477283917751
2012	1.0893369663696957
2013	1.0500433500953703
2014	1.1027912453218298
2015	0.9642313765594173
2016	0.8749265319067454
2017	0.8106742309760079
2018	0.8234649774347855
2019	0.713229893250757
2020	0.6681753188870545
2021	0.8407959567881031
2022	0.8681636136961765