Year	%
2000	34.1
2001	33.6
2002	33.7
2003	33.5
2004	33.9
2005	33.9
2006	33.9
2007	33.9
2008	35.6
2009	35.6
2010	33.9
2011	32
2012	31.3
2013	30.3
2014	30.5
2015	30.6
2016	30.5
2017	30
2018	28.1
2019	28