Year % of population 2001 6.1 2002 5.9 2003 6.3 2004 5.9 2005 5.9 2006 5.1 2007 5.1 2008 4.7 2009 3.9 2010 3.2 2011 2.5 2012 2.5 2013 2.5 2014 2.5 2015 2.5 2016 2.6 2017 2.6 2018 2.5 2019 2.5 2020 2.5 2021 2.5