Year	% of revenue
1973	22.72340425531915
1974	24.26520079942961
1975	21.05544663677488
1976	24.444560719443828
1977	24.29650149887957
1978	23.487939691093096
1979	23.708189985431844
1980	25.173303430877844
1981	22.94352003749707
1982	23.868354430379746
1983	23.344123505976082
1984	23.0006526951842
1985	24.49056974109166
1986	22.37398408443099
1987	26.676279328377117
1988	27.17385076433574
1990	23.499696269826984
1991	28.025420633590276
1992	24.755741973411986
1993	22.251663456443048
1994	21.124102680815128
1995	23.304886323516264
1996	21.863119514029314
1997	23.251639935899412
1998	22.609303664706122
1999	22.39382225920121
2000	24.280869874842494
2001	24.21570531206783
2002	22.627784274546276
2003	23.232911843736893
2004	23.187661143147537
2005	22.819230478332216
2006	24.574813747691906
2007	25.204903961231334
2008	25.14793369393412
2009	22.85401388647519
2010	21.280635061545876
2011	21.86891848283134
2012	20.528187617358647
2013	20.966219411359706
2014	22.189092535241286
2015	22.410846980948573
2016	23.114955252547446
2017	22.40566815681258
2018	24.146099564601517
2019	23.43159211254108
2020	22.480164305432424
2021	25.713742861198035
2022	25.2760595528815