Year	% of revenue
1973	2.395752395752398
1974	1.6609073681863742
1975	1.3787119166988033
1976	1.3808686919407533
1977	1.2931358544470255
1978	1.3429823951012398
1979	1.4744874862575232
1980	1.5582575847007485
1981	1.4035087719298238
1982	1.2687549355093446
1983	1.163773810115877
1984	1.2079045272261641
1985	1.1570779190963738
1986	1.2369384656604414
1987	1.3294925769997774
1988	1.3262254583279058
1989	1.4479559543937266
1990	1.5516318887105414
1991	1.6762664303647912
1992	1.8273020422787432
1993	1.9754698182567663
1994	2.094867063085236
1995	2.356764916550497
1996	2.430235113161942
1997	2.219312878771882
1998	2.285361334156887
1999	2.4985257146404294
2000	2.539192385314204
2001	1.9854408375111237
2002	2.158905005998473
2003	1.9474081894033985
2004	1.9425859091426148
2005	2.1314806705405953
2006	1.9748789346246975
2007	2.06970509383378
2008	2.002366939102946
2009	2.205876132547142
2010	2.188738705468154
2011	2.173097026521955
2012	1.9575374769073621
2013	2.4632897334649555
2014	2.9374822123138222
2015	2.651596577173868
2016	2.6264906088944153
2017	2.611515957355432
2018	2.5490061394642933
2019	2.3627381530551954
2020	2.8053891178609773
2021	2.555941051023331
2022	2.140796078896399