Year	%
2000	21.3
2001	21.3
2002	20.8
2003	20.1
2004	19.1
2005	19.1
2006	19.1
2007	19.2
2008	19.1
2009	18.2
2010	18
2011	17.1
2012	16.7
2013	16.2
2014	16.3
2015	16.5
2016	16.6
2017	16.7
2018	16.7
2019	16.7