Year % 2004 3.3 2005 2.6 2006 3.4 2007 3.5 2008 3.6 2009 3.6 2010 3.2 2011 3.1 2012 2.9 2013 2.9 2014 2.9 2015 3 2016 3.1 2017 3 2018 3.1 2019 3.1 2020 3.1 2021 3.5