Year	% of revenue
1972	16.686638705811863
1973	16.43872351836955
1974	19.300546448087367
1975	16.634391944229346
1976	17.999362854412272
1977	18.483547925607965
1978	17.385274836106902
1979	16.9408767646747
1980	17.530908120608437
1981	17.799176826900727
1982	17.740641711229934
1983	17.679062537366928
1984	17.567567567567536
1985	16.86874810548651
1986	17.535341996287283
1987	17.7558201640014
1988	17.074878717570137
1989	17.181656172032778
1990	17.124752178954854
1991	17.79339224245005
1992	16.8596812666367
1993	17.07342118774604
1994	17.442205586518455
1995	16.15144924182825
1996	16.884539773216538
1997	18.222807621712008
1998	23.293044680818248
1999	24.24430675669048
2000	25.301568392630593
2001	25.784784160771128
2002	24.277570101795927
2003	23.782887891745823
2004	24.11864126025105
2005	24.369819027018313
2006	25.25546126770865
2007	25.204903961231334
2008	25.831884168905194
2009	23.063928147534934
2010	23.246855938998557
2011	24.427659385200005
2012	25.490449941076243
2013	25.863423084485117
2014	25.435221869220527
2015	25.48822447952508
2016	25.283251756556762
2017	25.68204649582596
2018	27.454626101486873
2019	28.245990310094076
2020	28.60200295674376
2021	28.362111157925273
2022	29.76625159727461