Year	%
2000	24.1
2001	23.7
2002	23.2
2003	22.7
2004	22.4
2005	22.1
2006	21.6
2007	21.1
2008	20.6
2009	20.1
2010	20
2011	19.8
2012	19.6
2013	19.5
2014	19.3
2015	19.2
2016	19.1
2017	18.9
2018	18.9
2019	18.8