Year	%
2000	17.4
2001	17.2
2002	17
2003	16.9
2004	16.6
2005	16.5
2006	16.3
2007	16.3
2008	16.1
2009	15.9
2010	15.7
2011	15.8
2012	15.7
2013	15.6
2014	15.6
2015	15.5
2016	15.5
2017	15.4
2018	15.2
2019	15.2