Year	% of population
2001	15.6
2002	16.5
2003	17.7
2004	18.7
2005	20.3
2006	22.4
2007	26.1
2008	30.6
2009	31.9
2010	30.4
2011	25.9
2012	23.4
2013	21.8
2014	21
2015	20.3
2016	19.3
2017	18.9
2018	18.2
2019	17.6
2020	17.1
2021	17.1