Year	%
2000	28.7
2001	27.8
2002	26.5
2003	26.5
2004	26.4
2005	25.2
2006	23.6
2007	23
2008	23.6
2009	21.7
2010	21.9
2011	21.2
2012	20.1
2013	20.3
2014	19.8
2015	19.3
2016	18.8
2017	18.2
2018	17.6
2019	17.1