Year % of population 2001 18.4 2002 16.9 2003 16 2004 15.9 2005 16.9 2006 18.5 2007 20.1 2008 20.7 2009 19.4 2010 18.4 2011 18 2012 19.3 2013 21.3 2014 24.7 2015 30.2 2016 34.2 2017 35.5 2018 34.1 2019 32.5 2020 31.5 2021 31.6