Year	%
2000	37.6
2001	37
2002	36.4
2003	35.8
2004	34.9
2005	34.3
2006	33.7
2007	33.1
2008	32.5
2009	32.4
2010	32.5
2011	32.8
2012	33.2
2013	33.8
2014	34.4
2015	35.1
2016	35.8
2017	36.6
2018	37.3
2019	38