Year	%
2000	38.3
2001	37.9
2002	37.5
2003	37.3
2004	37.3
2005	37
2006	36.7
2007	36.4
2008	36
2009	35.6
2010	35.2
2011	34.9
2012	34.6
2013	34.3
2014	34
2015	33.7
2016	33.5
2017	33.3
2018	33.1
2019	33