Year	% of revenue
1998	12.48143010230497
1999	13.391152874913189
2000	13.830067673485312
2001	13.260456273764259
2002	13.764823852893098
2003	12.500000000000005
2004	11.59383239761722
2005	11.575113202321448
2006	13.802996321130005
2007	14.377382492081455
2008	15.639559218781102
2009	15.826001500626226
2010	14.782645374287414
2011	14.630512950628704
2012	14.042440173562937
2013	14.296234272837342
2014	15.249102630512667
2015	15.761828952572326
2016	15.284102386929034
2017	16.536558157956303
2018	16.78979988972189
2019	16.112305552443274
2020	15.827965945395857
2021	14.826156514413695
2022	14.43909022997838