Year % 2005 21.5459003039343 2006 22.9249264237646 2007 22.4772305345731 2008 20.4053322129654 2009 20.9948105298055 2010 17.7525801579801 2011 14.9437272531709 2012 13.5296315420868 2013 12.6409406273296 2014 11.6291669717805 2015 11.8584501648748 2016 12.9515014151532 2017 12.7606199307314 2018 12.5027652041209 2019 11.8586401367831 2020 11.5039275348061