Year	% of revenue
1972	20
1973	10.526315789473683
1974	15.384615384615385
1975	9.523809523809524
1976	9.67741935483871
1977	18.88888888888889
1978	15.277777777777779
1979	11.147540983606557
1980	12.625538020086083
1981	21.139240506329113
1982	21.68327215521762
1983	36.840205720472795
1984	31.676278620022792
1985	23.642291480698272
1986	22.91728227928999
1987	25.971024313801415
1988	20.469330787389428
1989	20.966513322977658
1990	19.542968813482197
1991	19.31582136056777
1992	16.151943511724635
1993	16.115333308856826
1994	15.181477105486806
1995	14.830552932535934
1996	13.713445802163088
1997	12.504870741694187
1998	13.249917184385335
1999	12.374268249296549
2000	13.31765231531292
2001	14.06351124908665
2002	21.250547981568975
2003	13.261408421607568
2004	14.520696728839786
2005	15.038413954118038
2006	12.889204178999872
2007	12.724789151302316
2008	15.103347772105996
2009	15.27410671809977
2010	11.975906834111179
2011	11.923550959064148
2012	10.794548355017533
2013	10.370877720686538
2014	7.170518247757025
2015	6.108544093183455
2016	6.264880413436093
2017	6.231785788150385
2018	7.189811567988643
2019	6.449580887912311
2020	6.182322541613749
2021	8.174641780346965
2022	9.773777390174617