Year	% of revenue
1998	40.05293672800605
1999	38.921794753513545
2000	33.67496538430212
2001	33.09078309078309
2002	39.23721091682214
2003	43.25925285368385
2004	41.6081812713054
2005	44.32152054844209
2006	44.59467544122046
2007	42.55836945775344
2008	40.653267465204934
2009	38.56431401949234
2010	40.46586423663564
2011	34.610376751507566
2012	42.546665541697074
2013	42.780874617256806
2014	42.78295186504436
2015	43.05801420252975
2016	39.74983718962284
2017	39.016362626666634
2018	40.16420708842385
2019	40.69786596780232
2020	40.27984805500793
2021	37.2163019604653