Year	%
2000	18.4
2001	18.2
2002	18.4
2003	18.2
2004	18.2
2005	18.7
2006	18.7
2007	18.2
2008	17.7
2009	17.6
2010	17.7
2011	16.9
2012	16.6
2013	16.5
2014	16.2
2015	16.1
2016	16.1
2017	16.2
2018	16.3
2019	16.2