Year	% of revenue
1973	21.86531417300648
1974	26.636225266362253
1975	26.464478604071456
1976	36.77596144760465
1977	32.08319127173542
1978	22.964103395186775
1979	21.939351198871652
1980	15.292105698681524
1981	17.486734201640136
1982	16.5639882902958
1983	13.236624342524037
1984	12.91007860155989
1985	10.634844614729671
1986	8.135189049136725
1987	9.617275476318571
1988	10.531042327725558
1989	12.731713020095867
1990	13.68262009509843
1991	13.630690919096331
1992	13.727725550722605
1993	11.772980098382794
1994	10.537652574228154
1995	12.308636921817438
1996	13.429685957614831
1997	12.471100157040656
1998	11.726622207077837
1999	11.885372188229079
2000	11.410804816223068
2001	11.884994270831296
2002	12.403219107326061
2003	12.03314774672675
2004	12.58751250178597
2005	14.775777762568538
2006	17.47266423682105
2007	16.45893595432448
2008	18.164707663510242
2009	22.160021905328993
2010	19.941318764041448
2011	18.206378254528634
2012	17.947428644312456
2013	18.773009318110528
2014	18.809801864789037
2015	19.214321677411384
2016	19.24007277604858
2017	20.77645472724793
2018	20.75385059323109
2019	23.16617857756727
2020	23.935826942456327
2021	24.674812884572653
2022	23.688556377258973