Year	%
2000	21.4
2001	20.7
2002	20.5
2003	20
2004	19.7
2005	19.6
2006	19.2
2007	19.4
2008	19.2
2009	19.1
2010	19.1
2011	19.1
2012	19
2013	18.9
2014	18.9
2015	18.9
2016	18.8
2017	18.6
2018	18.5
2019	18.3