Year	%
2000	23.2
2001	22
2002	21.5
2003	21.7
2004	21.1
2005	20.4
2006	20
2007	19.6
2008	19.7
2009	19.5
2010	18.9
2011	18.6
2012	18.2
2013	17.4
2014	17.7
2015	17.7
2016	18
2017	18.1
2018	18.1
2019	18.4