Year	% of population
1997	37
1998	36
1999	36.9
2000	36.3
2001	37.3
2002	36.7
2003	35.4
2004	35.6
2005	36.4
2006	35.3
2007	33.7
2008	32.3
2009	31.1
2010	29.6
2011	29.6
2012	28.7
2013	28.3
2014	27.7
2015	27
2016	27.5
2017	27.5
2018	26.3
2019	25.8
2020	28.9
2021	24.8
2022	25