Year	% of population
1990	28.5
1992	30.8
1997	34.1
1999	37.9
2000	38.2
2001	35.2
2002	35.9
2004	31.1
2005	33.7
2006	33.1
2007	34
2008	29.9
2009	28.9
2011	26.5
2012	27.7
2013	27.5
2014	26.4
2015	26.6
2016	26.8
2017	26.7
2018	24.7
2019	22.7
2020	22.8
2021	23