Year	%
2000	20.4
2001	20.2
2002	20.3
2003	20
2004	19.3
2005	18.8
2006	18.3
2007	18.8
2008	18
2009	17.8
2010	17.8
2011	17.6
2012	17.4
2013	17
2014	16.4
2015	16.5
2016	16.8
2017	16.2
2018	16.1
2019	15.7