Year	%
2000	22.7
2001	21.9
2002	21.7
2003	21.5
2004	21.1
2005	20.6
2006	19.9
2007	19.3
2008	18.8
2009	18.3
2010	18.2
2011	16.9
2012	16.7
2013	16.1
2014	16.2
2015	16
2016	15.9
2017	16.4
2018	15.9
2019	15.9