Year	%
1979	23.3
1986	23.3
1992	22.9
1997	22.9
2001	23
2002	23.2
2003	23.3
2004	23.6
2005	23.1
2006	23.3
2007	23.3
2008	23.3
2009	23.5
2010	22.9
2011	23.6
2012	23.5
2013	23.5
2014	23.5
2015	23.4
2016	23.6
2017	24
2018	23.6
2019	23.8
2020	23.8
2021	23.7