Year	% of revenue
1976	1.858577227088229
1977	1.4714111721913163
1978	2.5467808436409767
1979	3.051933862626557
1980	1.974070979918933
1981	2.5039580034997084
1988	30.710636692736504
1989	27.850623434083456
1990	30.32466346029981
1991	27.466007112638618
1992	29.175010966256842
1993	29.381004152534217
1994	33.669515446291356
1995	30.68087051492808
1996	43.243468137322715
1997	36.97921810499313
1998	46.68114835442358
1999	46.003253475992345
2000	42.486453151053034
2001	32.8398380043712
2002	34.73152909114135
2003	36.516007954080074
2004	32.52122358657699
2005	27.765586478706833
2006	26.182562368025057
2007	23.41097211441585
2008	25.198165246120713
2009	35.638265483632665
2010	23.84331592708236
2011	21.771835535451082
2012	21.227040690614462
2013	16.34666607802308
2014	17.63336465806259
2015	16.58189617176238
2016	19.063998012028314
2017	16.088364252758193
2018	15.27560123405813
2019	16.69498612764433
2020	22.425724145524168