Year	%
2000	37.6
2001	37.4
2002	37.1
2003	36.9
2004	36.6
2005	36.4
2006	36.2
2007	35.8
2008	35.4
2009	34.5
2010	34.7
2011	34.4
2012	34.2
2013	33.8
2014	33.9
2015	33.8
2016	33.6
2017	33.4
2018	33.3
2019	33.1