Year	%
2000	17.9
2001	17.3
2002	16.9
2003	16.5
2004	16.4
2005	15.5
2006	15.4
2007	15.1
2008	15.1
2009	14.7
2010	14.5
2011	14.5
2012	14
2013	13.7
2014	13.3
2015	13.3
2016	13.3
2017	13
2018	12.8
2019	12.7