Year	%
2000	23
2001	22.7
2002	22.7
2003	22.7
2004	22.5
2005	21.8
2006	20.7
2007	20
2008	19.6
2009	19.3
2010	19
2011	18.7
2012	18.3
2013	17.7
2014	17.2
2015	16.8
2016	16.6
2017	16.3
2018	16
2019	15.9