Year	%
2000	21
2001	20.1
2002	19.2
2003	18.9
2004	18.5
2005	18.2
2006	18.4
2007	18.9
2008	19.5
2009	19.2
2010	18.7
2011	18.8
2012	18.2
2013	18
2014	17.5
2015	17.3
2016	17.5
2017	17.2
2018	16.9
2019	16.8