Year	% of revenue
1997	17.410244855039807
1998	10.852698132342166
1999	12.103232162572322
2000	12.340199279022533
2001	11.07487971429624
2002	13.881324172346773
2003	13.460142047093907
2004	14.524646921711442
2005	11.487330028284422
2006	12.753757319324691
2007	12.367534618787495
2008	13.657808528284255
2009	10.553605992415063
2010	11.538769907797587
2011	12.60266706382376
2012	13.140216891535218
2013	13.877969516594746
2014	13.813682071934341
2015	14.919001918127659
2016	14.828628841159407
2017	15.39998160476813
2018	15.247634693567818
2019	15.195247719834121
2020	14.59209960888505
2021	14.082042546031948
2022	13.412494295866484