Year % of revenue 2009 6.52820101118947 2010 5.848062838375485 2011 6.424932552098642 2012 6.9705556140282745 2013 6.9516607142750955 2014 7.975607909618832 2015 7.585271755954351 2016 6.868034039539017 2017 6.979801181995226 2018 7.568959786145349 2019 7.795172127926898 2020 6.692490497516126 2021 6.578693396170708 2022 7.46025146954536