Year	%
2003	26.8
2004	28
2005	29
2006	30.2
2007	29.5
2008	31.8
2009	28.7
2010	26.2
2011	26.8
2012	26.8
2013	25.4
2014	27.8
2015	26.8
2016	27.2
2017	26.1