Year	% of revenue
1981	38.31573896353167
1982	40.87075450193755
1983	38.720330237358105
1984	32.585949177877424
1985	31.81733803601262
1986	29.614370468029005
1987	31.08721986674742
1988	40.20762121787568
1989	32.401992635910766
1990	31.331946830635683
1991	25.60816326530612
1992	27.40356937248129
1993	27.557755775577558
1994	26.779333655239014
1995	29.267030442796056
1996	28.82607678972013
1997	31.11408941503418
1998	33.501738123124134
1999	34.58628126021135
2000	35.45126884251753
2001	33.915529422005235
2002	33.78272469925182
2003	36.0073773673182
2004	38.22371290492409
2005	37.207839473462286
2006	35.23227792959717
2007	34.484533933549116
2008	32.02176081969449
2009	33.45867850246979
2010	37.18234523828327
2011	37.757749759176754
2012	37.502060319617705
2013	36.9518681881404
2014	36.949630427898384
2015	36.40801293055539
2016	36.432875924788696
2017	36.3963698860098
2018	37.4125972219899
2019	36.99035680580485
2020	37.784999871397645
2021	39.104961381303326
2022	40.14182363160372