Year	% of revenue
2001	31.061801619912643
2002	29.93069650365384
2003	25.13062394933685
2004	32.55843382948942
2005	32.388647432922994
2006	30.915205261609728
2007	27.092673835919683
2008	26.547633451163893
2009	24.346461981699502
2010	24.29535217423265
2011	24.555880940862618
2012	23.423599742469232
2013	20.56561170241501
2014	20.446922085139533
2015	23.725919294548444
2016	24.54659161976235
2017	10.121360382253231
2018	9.966875526876128
2019	9.273535573288791
2020	8.607704287268483
2021	9.317768839550961