Year	% of revenue
1972	2.5454155725845347
1973	2.603304822057007
1974	2.882320543418395
1975	2.47429709507832
1976	4.139255629659877
1977	4.847335996208788
1978	5.6114551083591335
1979	6.574867576762414
1980	6.652887992991588
1981	5.981015574601419
1982	5.677661606189104
1983	5.7847224576031815
1984	5.763117486044135
1985	5.932944346305515
1986	7.256697738087478
1987	7.365815113097161
1988	6.059244803652632
1989	6.285227444753862
1990	5.974415024532004
1991	5.378140859017205
1992	5.616603707502564
1993	6.2052870021508
1994	6.01765513932481
1995	5.237829265616741
1996	4.58601493791388
1997	3.9549492084528035
1998	3.9597854219018513
1999	3.2432057083122983
2000	2.7150028976602267
2001	3.2326340006180683
2002	3.0370311740912785
2003	3.5306888949421458
2004	2.9122540257873366
2005	2.977234737337825
2006	4.241453959086978
2007	4.38855311455929
2008	3.1947906598158418
2009	2.2856836700215952
2010	1.8261398454590936
2011	1.4864850038582929
2012	1.0342457171220278
2013	0.9954985847002215
2014	0.9374375099122207
2015	0.961324598028644
2016	0.8198072011205405
2017	0.6780550959745143
2018	0.7042283063701769
2019	0.6825081163127346
2020	0.7165339596044753
2021	0.4312035833563604
2022	0.4780574253423912