Year	% of revenue
1972	26.824131187001655
1973	22.72340425531915
1974	21.629816803537587
1975	21.414852752880922
1976	25.146484375
1977	23.541947858208427
1978	18.655027481409633
1979	18.286606231614336
1980	18.072289156626507
1981	15.935043055035566
1982	15.019058667550548
1983	14.522943532091553
1984	15.788963869426237
1985	19.359351357524197
1986	16.002967437670563
1987	17.600838135149292
1988	17.497899159663866
1989	19.45227623021691
1990	17.88372828856434
1991	12.50860232672456
1992	6.889715399865646
1993	6.028882206630286
1994	5.544590643274853
1995	13.041318582072703
1996	11.818901334764236
1997	13.45345942227448
1998	12.816159484391243
1999	14.647849773965458
2000	17.397934049945878
2001	12.985225530066904
2002	10.047773368224643
2003	10.714265945304447
2004	12.95682776359354
2005	15.593718360057446
2006	17.22760266979014
2007	17.738864214565993
2008	13.97845947949763
2009	13.034485027794155
2010	14.856628950285486
2011	14.132033625117938
2012	12.442035342774783
2013	12.908243486975557
2014	14.095565133092727
2015	15.884563257871829
2016	15.731937251410072
2017	16.23594703203633
2018	15.56182195686856
2019	15.502070254150818
2020	15.012575652801832
2021	16.887553385362324
2022	16.293745804798373