Year % of revenue 2009 24.816906697326267 2010 26.358543927573997 2011 30.404488246943156 2012 35.23941994329657 2013 27.947459771563082 2014 35.60667040563049 2015 38.73586364343343 2016 38.249778736947874 2017 38.59017219789444 2018 42.0209627367394 2019 40.67662171178607 2020 40.03883172431733 2021 38.40077910240156 2022 35.75919270537856