Year % 2008 14.4959695093475 2009 14.7656072014188 2010 13.6500697343973 2011 15.4989623589473 2012 15.2550150731634 2013 13.5084390852533 2014 13.6661894541378 2015 14.0710956479358 2016 14.4380562061415 2017 13.8421504299584 2018 16.1672672662752