Year	%
2000	16.1
2001	15.9
2002	15.8
2003	15.7
2004	15.6
2005	15.5
2006	15.4
2007	15.3
2008	15.2
2009	15.2
2010	15.1
2011	15.1
2012	15.1
2013	15.2
2014	15.2
2015	15.3
2016	15.4
2017	15.5
2018	15.7
2019	15.9