Year	%
2000	20.1
2001	19.9
2002	19.9
2003	19.8
2004	19.7
2005	20.3
2006	20.4
2007	20.8
2008	20.7
2009	20.6
2010	20.6
2011	20.3
2012	20.2
2013	20.4
2014	20.2
2015	19.9
2016	19.5
2017	19.4
2018	19.6
2019	19.6