Year	%
2000	36.5
2001	35.9
2002	35.3
2003	34.9
2004	34.6
2005	34.4
2006	34.1
2007	33.9
2008	33.6
2009	33.4
2010	33.3
2011	33.3
2012	33.4
2013	33.5
2014	33.6
2015	33.8
2016	34.1
2017	34.3
2018	34.5
2019	34.6