Year	% of population
1980	17.5
1985	16.7
1990	14.2
1993	17.5
1994	18
1995	16.2
1996	18.7
1997	16.5
1998	16.5
1999	14.7
2000	15.2
2003	15.6
2004	15.4
2005	15.3
2006	16
2007	15.6
2008	16.5
2009	16.9
2010	16.8
2011	17.7
2012	18
2013	19.9
2014	19.5
2015	19
2016	18.7
2017	17.9
2018	17.5
2019	17.5
2020	17.9
2021	16.9