Year	% of revenue
1973	23.16757316757317
1974	21.290825994872336
1975	20.931353644427293
1976	21.37417357101022
1977	22.532140440568263
1978	22.775033052675596
1979	22.350126107482367
1980	21.797898713257094
1981	20.56808688387633
1982	19.847328244274763
1983	19.938329934848493
1984	20.679325506112068
1985	20.70802148858997
1986	21.420916316870464
1987	22.831819189009536
1988	23.08325748710609
1989	23.240993627259755
1990	23.447339177676255
1991	22.153300841825445
1992	22.49372984593338
1993	22.21115195657399
1994	23.13239013054481
1995	24.758354577592247
1996	25.295539441880905
1997	26.01023431945999
1998	26.698579369981466
1999	27.519165709674414
2000	27.09609145950072
2001	28.7021120182183
2002	29.170029447049846
2003	29.41100816153735
2004	29.54364484338321
2005	29.49237105083178
2006	28.676470588235293
2007	28.492010723860588
2008	27.1717460544396
2009	27.13206493693267
2010	26.75644844933566
2011	26.029537006017993
2012	25.260852043523883
2013	25.001156836130306
2014	25.555450147044873
2015	25.899359257206
2016	26.545596998296446
2017	26.47007287232398
2018	26.785661717807063
2019	27.488562157212726
2020	27.82089589833849
2021	27.92350406699326
2022	25.892723032530927