Year	% of revenue
1972	17.94945433658817
1973	18.65284974093264
1974	19.875776397515526
1975	18.55911150080374
1976	20
1977	16.13287650826754
1978	16.386925795053003
1979	17.96693537368493
1980	19.25150650174437
1981	18.920841377908747
1982	21.707793794282924
1983	19.78099969583291
1984	19.144554455445544
1985	19.02322603178299
1986	16.6387515829895
1987	15.921241361324814
1988	17.21549081353882
1989	20.657804711171927
1990	21.254479306288808
1991	21.227808621367746
1992	14.673839509446829
1993	14.582749697300635
1994	14.110623228831617
1995	15.569692801467216
1996	16.391777370179867
1997	16.471641251775758
1998	16.424004767405076
1999	17.94550920788431
2000	17.905001032478296
2001	22.51935545366283
2002	21.24354149721348
2003	24.203974361844143
2004	18.334391629017823
2005	17.956838937753716
2006	19.839161829277156
2007	22.408371836233183
2008	22.449454858968014
2009	21.789496110783325
2010	18.735951232473184
2011	20.491290700671524
2012	26.086676669546716
2013	27.1587389183577
2014	28.230172070984743
2015	20.97073236006329
2016	25.258799392409237
2017	26.497909230426636
2018	26.113623351018767
2019	27.151926375640013
2020	27.968764607240903
2021	29.666980348641886
2022	27.357152197118694