Year	% of population
1997	55.6
1998	49
1999	42.8
2000	41.6
2001	31.1
2002	41.1
2003	54
2004	53.1
2005	42.4
2006	33.1
2007	27.5
2008	27.7
2009	26.4
2010	26.8
2011	27.4
2012	27.2
2013	29.4
2014	29.5
2015	33.1