Year	%
2000	19.5
2001	19.4
2002	19.2
2003	19.1
2004	18.9
2005	18.7
2006	18.4
2007	18.2
2008	17.9
2009	17.5
2010	17.3
2011	17.2
2012	17.1
2013	17.1
2014	17.1
2015	17.1
2016	17.2
2017	17.3
2018	17.4
2019	17.6