Year	%
2000	36.9
2001	36.3
2002	36.2
2003	35.8
2004	35.4
2005	34.8
2006	35
2007	34.6
2008	34.2
2009	34.7
2010	34.7
2011	34.5
2012	34
2013	34
2014	33.3
2015	33.4
2016	32.6
2017	32.3
2018	32.1
2019	31.8