Year	% of revenue
2012	29.854723735498244
2013	30.749381479759343
2014	32.49616466229761
2015	33.464630811723836
2016	37.00234673333946
2017	33.806519166029354
2018	35.881540835394205
2019	35.7341881490391
2020	36.19831750561488
2021	37.49667057822198