Year	%
2000	23.7
2001	21.2
2002	20.6
2003	20.1
2004	20.3
2005	19.5
2006	19
2007	18.3
2008	17.8
2009	17.6
2010	17.7
2011	17.5
2012	17.3
2013	17
2014	17.1
2015	17.2
2016	17.4
2017	17.3
2018	17.2
2019	17.2