Year % of revenue 2012 7.4605799546230696 2013 11.23290580178672 2014 12.958217726834603 2015 10.643704589094988 2016 15.855262142078466 2017 14.87709180492387 2018 10.201244153080841 2019 10.618119695372073 2020 10.556664998885608 2021 13.95133991901022