Year % of internal resources 2006 16.46972860125261 2007 17.013778705636742 2008 17.221085594989564 2009 17.026304801670143 2010 17.384759916492694 2011 17.54885177453027 2012 17.588308977035492 2013 17.629853862212943 2014 17.626722338204594 2015 18.03757828810021 2016 18.18580375782881 2017 19.163106471816285 2018 19.239626469728602 2019 17.92633549895616 2020 17.92633549895616