Year	% of population
1981	39.6
1986	31.6
1989	31.1
1990	29.6
1991	32.1
1992	30.1
1993	29.4
1994	28.3
1995	28.6
1996	29.3
1997	29
1998	27.2
1999	28.4
2000	28.1
2001	27.7
2002	27.5
2003	27.1
2004	27.2
2005	26
2006	26
2007	24.5
2008	24.2
2009	25.9
2010	23.9
2011	25.8
2012	24.9
2013	24.1
2014	24.9
2015	23.7
2016	24.6
2017	23.4
2018	23.6
2019	24
2020	25.7
2021	24.6
2022	23.8