Year	%
2000	37.1
2001	36.8
2002	36.3
2003	35.6
2004	35.1
2005	34.6
2006	34
2007	33.5
2008	33
2009	32.5
2010	32.1
2011	31.8
2012	31.4
2013	31.3
2014	31.2
2015	31.2
2016	31.1
2017	31.1
2018	31
2019	31