Year	%
2000	34.5
2001	34.2
2002	33.8
2003	33.8
2004	33.7
2005	33.8
2006	33.7
2007	33.9
2008	33.8
2009	33.7
2010	33.7
2011	33.5
2012	33.3
2013	32.9
2014	32.8
2015	32.6
2016	32.2
2017	31.7
2018	31.6
2019	31.3