Year	% of revenue
1972	4.1522491349480966
1973	5.6028368794326235
1974	6.961465571699304
1975	6.7648314127187374
1976	6.7626953125
1977	7.160616608652412
1978	6.9123827998706755
1979	3.8302215284865224
1980	3.6037483266398924
1981	4.12298764507675
1982	4.072754391779914
1983	5.077335684632058
1984	6.8806302670239905
1985	6.652011305564279
1986	7.1509948864690145
1987	9.536064864372424
1988	9.596638655462185
1989	6.965903537460997
1990	6.784459358190811
1991	7.483204981156807
1992	6.870053905264366
1993	6.071574414374281
1994	4.078947368421053
1995	23.90565025965229
1996	26.437990475551683
1997	25.884586543313926
1998	31.46764799488844
1999	31.851512692708937
2000	29.02084191233093
2001	31.24126356550573
2002	32.954265809403324
2003	32.41591026590545
2004	31.453997815183005
2005	29.864802100357768
2006	29.38744508651222
2007	28.417834504764777
2008	29.577274596050735
2009	29.070080754670673
2010	28.095371551670045
2011	28.68380792011741
2012	30.00540893529726
2013	29.998779385099184
2014	29.983219843411163
2015	29.24146486629904
2016	29.657130289953415
2017	29.89053579172076
2018	30.00422178527741
2019	29.89594036520395
2020	29.212048148533455
2021	29.149256430588594
2022	28.20692972699006