Year	% of revenue
1972	1.250746714456392
1973	1.3711011442896366
1974	1.3959296534704981
1975	1.6507116588529238
1976	2.057232175063124
1977	3.4001068667328225
1978	3.708662596906483
1979	6.563298604285434
1980	7.436904260117873
1981	10.520310052395613
1982	12.947709783583122
1983	15.169205794205794
1984	18.597330252511004
1985	19.057420287200966
1986	16.35570427158559
1987	15.815544766712986
1988	15.13533984322713
1989	14.781045006711748
1990	15.493811838413418
1991	15.401252240589525
1992	13.44229690003402
1993	14.521000458951338
1994	14.015328906120047
1995	14.419190212671168
1996	13.773029051492042
1997	12.557321468338554
1998	11.2302246307141
1999	10.242837993703045
2000	9.313266557244763
2001	8.646391206875077
2002	8.054347595919694
2003	7.20748883154676
2004	6.1969518777440165
2005	4.7917358571939
2006	4.22677118914801
2007	3.526877634891056
2008	3.0701529676160617
2009	4.3455644676804415
2010	4.382972946013942
2011	4.455168265214049
2012	4.074797292995906
2013	3.855098264330987
2014	3.2270808887543057
2015	3.7388243689987903
2016	3.2795209627843422
2017	1.8828794475233765
2018	1.9642219749301866
2019	1.6796811278150299
2020	1.2505299537933958
2021	1.2024886137670296
2022	1.7551972900312278