Year % of expense 2008 1.519280328752254 2009 2.1963525245249134 2010 2.412495724546802 2011 3.2768183835368716 2012 3.6668931092536257 2013 3.2485984068569924 2014 3.3008722371798767 2015 4.042913451780697 2016 5.174117920763121 2017 4.569505109185091 2018 5.310179267451929 2019 5.177437695113236 2020 4.721098284302233 2021 4.893296417197467 2022 4.097585641507811