Year	% of revenue
1998	41.78904135571459
1999	42.641564263025906
2000	41.91710014557074
2001	42.28331068657496
2003	44.525510204081634
2004	43.80033352168422
2005	41.77184313738016
2006	38.160996002876004
2007	40.34365321405176
2008	39.07812296592596
2009	38.56431401949234
2010	40.03975561289839
2011	36.349386041221024
2012	36.61142120013656
2013	35.86528215723531
2014	36.04931669094695
2015	37.05727125275827
2016	35.38559324590086
2017	33.45873152236196
2018	33.348220108620765
2019	30.340080614512328
2020	34.554626180891084
2021	34.79580984298643