Year	%
1979	26.9
1986	24.6
1991	25.2
1995	26
2000	27.4
2003	27.6
2004	31.6
2005	30.6
2006	26.4
2007	27.1
2008	27
2009	26.2
2010	25.7
2011	25.3
2012	25.7
2013	26.4
2014	26.8
2015	27.5
2016	28.5
2017	27
2018	27.6
2019	27.7