Year	%
2000	22
2001	21.9
2002	21.9
2003	21.5
2004	21.1
2005	21.7
2006	21.1
2007	21.9
2008	20.6
2009	20.5
2010	20.1
2011	19.7
2012	19.1
2013	19.1
2014	19
2015	19.2
2016	18.8
2017	18.7
2018	18.8
2019	18.7