Year	%
1979	36.7
1986	34.8
1991	35.3
1995	35.8
2000	37.1
2003	37.2
2004	40.5
2005	39.7
2006	35.5
2007	36.5
2008	36.2
2009	35.6
2010	35.3
2011	34.8
2012	35.2
2013	35.7
2014	35.9
2015	36.6
2016	37.2
2017	36
2018	36.6
2019	36.7