Year	% of population
1997	42.7
1998	42.4
1999	47.5
2000	48.4
2001	54.8
2002	54.3
2003	52.3
2004	58.7
2005	55.6
2006	49.2
2007	42.4
2008	37.3
2009	33.5
2010	30.8
2011	27.8
2012	25.8
2013	23.9
2014	22.7
2015	21.8
2016	20.7
2017	21.7
2018	20.5
2019	20.2
2020	30.1
2021	25.9
2022	27.5