Year % 2004 16.1 2005 14.4 2006 11.9 2007 13.1 2008 13.6 2009 16.1 2010 15.6 2011 13.9 2012 14.1 2013 13 2014 15 2015 14.7 2016 15 2017 13.5 2018 13.2 2019 12.1 2020 10.4 2021 11.2