Year % of population 2001 7.2 2002 5.5 2003 4.5 2004 3.8 2005 3.9 2006 3.9 2007 3.9 2008 3.5 2009 3.7 2010 4.2 2011 4.6 2012 4.3 2013 4 2014 3.6 2015 3.6 2016 3.7 2017 3.7 2018 3.1 2019 3.1 2020 3 2021 2.9