Year	%
2000	18.4
2001	18.2
2002	18.2
2003	18.4
2004	18.9
2005	18.9
2006	18.9
2007	18.8
2008	18.6
2009	18.5
2010	18.5
2011	18.7
2012	20.2
2013	20.3
2014	20.4
2015	20.5
2016	19.9
2017	19.9
2018	19.6
2019	19.4