Year	%
2000	18.9
2001	18.6
2002	18.3
2003	18.4
2004	18.1
2005	17.8
2006	17.5
2007	17.2
2008	16.9
2009	16.6
2010	16.2
2011	16
2012	15.8
2013	15.4
2014	15.2
2015	15.2
2016	15.2
2017	15.2
2018	14.9
2019	14.9