Year	%
2000	30.8
2001	30.3
2002	29.7
2003	29.3
2004	29.3
2005	29.3
2006	29.1
2007	29
2008	28.7
2009	28.5
2010	28.5
2011	28.5
2012	28.3
2013	28.1
2014	27.9
2015	27.7
2016	27.7
2017	27.5
2018	27.5
2019	27.5