Year % of population 2001 4 2002 3.8 2003 3.7 2004 3.6 2005 3.5 2006 3.5 2007 3.5 2008 3.7 2009 5.4 2010 6.9 2011 8.8 2012 8.8 2013 9.2 2014 8.9 2015 9.2 2016 8.9 2017 8.4 2018 6.9 2019 5.7 2020 5.9 2021 6.6