Year	%
2000	20
2001	19.5
2002	19.1
2003	18.6
2004	17.7
2005	17.1
2006	16.7
2007	16.3
2008	15.8
2009	15.2
2010	14.9
2011	14.2
2012	13.7
2013	13.7
2014	13.4
2015	13.4
2016	13.4
2017	12.7
2018	12.4
2019	12.1