Year	% of revenue
1991	26.510454217736125
1992	30.518633076554803
2009	24.739593726304026
2010	24.97118801807319
2011	26.386617944725483
2012	29.80191599878455
2013	31.53227729856501
2014	32.12624036689864
2015	32.82059467546608
2016	32.81748620742319
2017	31.753961767497714
2018	31.236280518305243
2019	31.759509890031204
2020	30.756557213825015
2021	32.47737245298934
2022	32.111365808560585