Year	% of revenue
1972	32.02025886325267
1973	27.772556390977442
1974	25.280247390800152
1975	27.685950413223143
1976	28.186714542190305
1977	29.745697405599795
1978	30.34564958283671
1979	30.61182729691017
1980	30.934799685781616
1981	30.396306271642942
1982	29.003755246299978
1983	34.705075445816185
1984	35.6300759758973
1985	40.56463595839524
1986	49.97598693689367
1987	53.989341160114314
1988	45.734699769053115
1989	38.77784850413749
1990	42.6253357206804
1991	40.13755710628043
1992	39.46168489087609
1993	43.22121373909948
1994	36.06742341356674
1995	38.416643132825
1996	43.10153943483762
1997	42.92304992101898
1998	47.8633585413861
1999	47.30225638482519
2000	42.15388955497567
2001	40.09649503484543
2002	40.0997150997151
2003	35.92870544090056
2004	38.214031436551835
2005	36.303442567829705
2006	33.89485638574741
2007	33.401276312029715
2008	32.625838176128745
2009	24.038122132015534
2010	23.79894357340488
2011	23.00246462741321
2012	22.29318239298177
2013	23.019036839320997
2014	24.773138231284946
2015	26.989529929390336
2016	27.929361251101863
2017	30.70280686754495
2018	28.45408420969197
2019	37.07661297307465
2020	29.47454960588704
2021	25.6311711527794
2022	25.81503444972138