Year	%
2000	25.5
2001	24.4
2002	23.2
2003	22.4
2004	21.2
2005	20.4
2006	20.5
2007	20.7
2008	21
2009	20.6
2010	19.9
2011	18.8
2012	17.9
2013	18.6
2014	18.2
2015	18.2
2016	18.4
2017	18.2
2018	18.1
2019	18.1