Year % 2000 15.16 2006 19.03 2008 19.91 2009 19.73 2010 20.21 2011 20.97 2012 19.65 2013 19.01 2014 18.37 2015 17.74 2016 17.01 2017 17.1 2018 17.01 2019 17.34 2020 16.57 2021 20.4