Year	%
2000	23.2
2001	22.8
2002	22.9
2003	22.9
2004	22.8
2005	23.3
2006	23.7
2007	23.4
2008	22.7
2009	22.1
2010	21.5
2011	20.2
2012	19.4
2013	19
2014	18.8
2015	18.6
2016	18.5
2017	18.8
2018	18.9
2019	18.9