Year	%
2000	36.5
2001	34.5
2002	34.7
2003	34.7
2004	34.5
2005	33.9
2006	33.1
2007	32.4
2008	31.5
2009	31.6
2010	31.1
2011	29.7
2012	28.9
2013	28.5
2014	28.2
2015	28.5
2016	27.9
2017	29.2
2018	28.3
2019	28.3