Year	%
2000	21.9
2001	21.9
2002	21.6
2003	21.4
2004	21.2
2005	20.7
2006	20.3
2007	20
2008	19.6
2009	19.2
2010	18.8
2011	18.7
2012	18.5
2013	18.3
2014	18
2015	17.8
2016	17.6
2017	17.3
2018	17.1
2019	16.9