Year	%
2000	19.4
2001	19.3
2002	19.2
2003	18.7
2004	17.8
2005	17.8
2006	17.8
2007	19.3
2008	18.8
2009	18.8
2010	17.8
2011	17.6
2012	17.7
2013	17.4
2014	18
2015	18.2
2016	18.4
2017	18.8
2018	19
2019	18.6