Year	%
2000	23.1
2001	22.7
2002	22.2
2003	21.9
2004	21.5
2005	21.2
2006	20.9
2007	20.6
2008	20.2
2009	19.9
2010	19.4
2011	19.3
2012	19.2
2013	19.1
2014	19
2015	18.9
2016	18.5
2017	18.7
2018	18.6
2019	18.5