Year % 2003 2.3 2004 2.4 2005 2.4 2006 2.5 2007 2.6 2008 2.6 2009 2.7 2010 2.7 2011 2.5 2012 2.2 2013 2.1 2014 2.3 2015 2.4 2016 2.4 2017 2.7 2018 2.8 2019 2.8 2020 2.4 2021 2.8