Year	%
2000	36.8
2001	36.5
2002	36.2
2003	36
2004	35.9
2005	35.6
2006	35.3
2007	35
2008	34.6
2009	34.2
2010	33.9
2011	33.6
2012	33.4
2013	33.2
2014	33.1
2015	33
2016	32.9
2017	32.8
2018	32.7
2019	32.6