Year % of population 2001 3.4 2002 3.2 2003 2.7 2004 2.5 2005 2.5 2006 2.5 2007 2.5 2008 2.5 2009 2.5 2010 2.5 2011 3 2012 2.8 2013 2.5 2014 2.5 2015 2.5 2016 2.5 2017 2.5 2018 2.5 2019 2.5 2020 2.5 2021 2.5