Year % 2004 20.6 2005 20.6 2006 20.4 2007 20.4 2008 20.1 2009 20.6 2010 20.7 2011 20.8 2012 21.1 2013 21.4 2014 21.2 2015 21.1 2016 20.6 2017 20.4 2018 21 2019 20.7 2020 20.5 2021 20.7