Year	%
2000	23.4
2001	20.3
2002	19.3
2003	18.8
2004	19.2
2005	18.2
2006	18
2007	17.5
2008	16.3
2009	17.1
2010	17.1
2011	16.6
2012	16.3
2013	16.1
2014	16.4
2015	16.4
2016	16
2017	16.2
2018	16.1
2019	16.5