Year	%
1979	22.5
1986	22.7
1991	22.4
1995	22.4
2000	22
2003	22
2004	21
2005	21.2
2006	23
2007	22.6
2008	22.8
2009	22.8
2010	22.8
2011	23
2012	22.9
2013	22.9
2014	22.8
2015	22.7
2016	22.5
2017	22.8
2018	22.6
2019	22.6