Year	%
2000	40.9
2001	40.6
2002	40.4
2003	40.2
2004	39.9
2005	39.5
2006	39.2
2007	38.8
2008	38.4
2009	38
2010	37.6
2011	37.3
2012	37
2013	36.9
2014	36.7
2015	36.6
2016	36.6
2017	36.5
2018	36.5
2019	36.5