Year	%
2000	38.8
2001	37
2002	37.4
2003	37.3
2004	37.6
2005	37.2
2006	36.6
2007	36.4
2008	36.9
2009	36.8
2010	36.3
2011	35.8
2012	35.1
2013	34.9
2014	34
2015	33.6
2016	33.1
2017	32.6
2018	32.2
2019	32.1