Year	%
2000	37.6
2001	37.4
2002	37.5
2003	37.5
2004	37
2005	37.5
2006	37.1
2007	36.5
2008	34.5
2009	33.6
2010	33.3
2011	32.1
2012	30.8
2013	30.4
2014	30.6
2015	31
2016	30.2
2017	30.8
2018	29.9
2019	29.6