Year	% of population
1986	30.2
1989	36.3
1992	31.1
1996	29.9
1997	29.7
2000	30.1
2001	29.6
2002	29.7
2003	31.4
2004	33.2
2005	30.8
2006	30.5
2007	29.4
2008	29.6
2009	28.9
2010	29.9
2011	28.4
2012	27.7
2013	27.7
2014	26.7
2015	26.3
2016	26.3
2017	22.2
2018	21.6
2019	21.5
2020	20.9
2021	20.4
2022	21.4