Year	% of population
2001	23.4
2002	23.6
2003	24.2
2004	23.5
2005	21.9
2006	20.1
2007	18.6
2008	18.3
2009	16.1
2010	14.2
2011	12.1
2012	12.4
2013	12.9
2014	13.3
2015	13.9
2016	14.3
2017	15.1
2018	15.7
2019	16.5
2020	17.2
2021	17.8