Year	%
2000	20.6
2001	20.2
2002	19.7
2003	19.2
2004	18.7
2005	18.1
2006	17.6
2007	17.1
2008	16.6
2009	16.1
2010	15.5
2011	15.3
2012	15.3
2013	15.3
2014	15.3
2015	15.4
2016	15.2
2017	15.1
2018	14.9
2019	14.8