Year	%
2000	20.5
2001	20.2
2002	20
2003	20.3
2004	19.8
2005	19.1
2006	18.9
2007	19.2
2008	18.3
2009	17.8
2010	17.6
2011	17.8
2012	17.4
2013	17
2014	17
2015	17.1
2016	17.5
2017	16.1
2018	16.9
2019	16.5