Year	%
2000	37.2
2001	37.1
2002	36.9
2003	36.9
2004	36.9
2005	37.1
2006	36.9
2007	36.8
2008	36.4
2009	36.2
2010	35.9
2011	35.8
2012	35.4
2013	34.9
2014	34.7
2015	34.4
2016	33.8
2017	33.2
2018	32.9
2019	32.6