Year	%
2000	19.3
2001	19.5
2002	19.5
2003	19.5
2004	19.3
2005	19
2006	18.9
2007	18.6
2008	18.5
2009	18.3
2010	17.9
2011	17.7
2012	17.6
2013	17.1
2014	16.7
2015	16.7
2016	16.4
2017	16.2
2018	16.1
2019	16