Year	% of revenue
1997	6.305607553381305
1998	5.567673683062494
1999	5.72907644184777
2000	5.213723206000759
2001	5.203171550683106
2002	5.592431456980266
2003	6.211727994872362
2004	5.288261468036748
2005	4.897248621246372
2006	3.7089951536543686
2007	3.9445588933789937
2008	2.9762188391702753
2009	2.49865623748617
2010	2.4532487645335017
2011	3.049694580690641
2012	2.955325683769086
2013	2.92589456587331
2014	2.8847501539637705
2015	2.990060685706969
2016	2.822963496375828
2017	2.726126816091257
2018	2.9814072211376996
2019	2.702074791965101
2020	2.63088723774295
2021	3.14616908878397
2022	2.8181115704639392