Year	%
2000	20.8
2001	20.2
2002	19.8
2003	19.3
2004	18.9
2005	18.7
2006	18.2
2007	18.3
2008	18.1
2009	18.1
2010	18
2011	18.1
2012	18
2013	18
2014	18.1
2015	18.2
2016	18.2
2017	18
2018	18
2019	17.9