Year	%
2000	55.4
2001	55.2
2002	54.9
2003	54.6
2004	54.3
2005	53.9
2006	53.6
2007	53.2
2008	52.9
2009	52.6
2010	52.4
2011	52.2
2012	52.1
2013	52
2014	51.9
2015	51.8
2016	51.8
2017	51.7
2018	51.6
2019	51.5