Year	%
2000	24
2001	23.7
2002	23
2003	22.5
2004	21.6
2005	21.6
2006	21.6
2007	21.4
2008	21.2
2009	20.3
2010	19.9
2011	19.2
2012	18.8
2013	18.7
2014	18.5
2015	18.5
2016	18.5
2017	18.7
2018	18.7
2019	18.5