Year	% of population
2001	31.6
2002	31.6
2003	30.3
2004	29.3
2005	28.3
2006	27.8
2007	26.7
2008	25.8
2009	23.3
2010	21.2
2011	19.6
2012	19.5
2013	19.2
2014	19.7
2015	19.8
2016	20.3
2017	20
2018	19.7
2019	18.8
2020	17.5
2021	17.4