Year	%
2000	59.9
2001	59.9
2002	59.9
2003	59.9
2004	59.8
2005	59.7
2006	59.6
2007	59.4
2008	59.2
2009	58.9
2010	58.7
2011	58.4
2012	58.1
2013	57.8
2014	57.5
2015	57.3
2016	57
2017	56.7
2018	56.4
2019	56.1