Year	%
2000	38
2001	37.4
2002	37.5
2003	37.6
2004	37.2
2005	37.3
2006	37.5
2007	37.3
2008	37.5
2009	37.3
2010	36.4
2011	35
2012	34.2
2013	33.5
2014	33.5
2015	33.6
2016	33.1
2017	32.7
2018	30.2
2019	28.5