Year	% of revenue
1991	18.16200916524396
1992	20.573927571126728
1993	17.696661661083514
1994	14.414988791312751
1995	18.9906926907158
1996	22.87383122541746
1997	24.873487878933926
1998	22.237077908351736
1999	23.799874244621755
2010	9.883705621626365
2011	11.584696402984797
2012	17.374282271516847
2013	14.529256270620502
2014	13.709641208943099
2015	17.146917426480357
2016	17.426264695507815
2017	14.898002354082763
2019	19.009850855369198
2020	17.89051786390787
2021	15.836317868726487