Year	% of revenue
2001	17.149761687998716
2002	19.85309677727642
2003	16.775796262174257
2004	15.678521965288855
2005	14.766803285327804
2006	8.963987765217198
2007	8.693045132168152
2008	8.008046516593822
2009	10.885843475585277
2010	10.020508807608467
2011	5.645456324391468
2012	10.829738489475984
2013	11.505547428868724
2014	11.116134855903445
2015	12.770141359136133
2016	14.871577133964866
2017	16.127184740919972
2018	14.56004250130202
2019	16.13024768992506