Year	%
2000	34.8
2001	34.3
2002	33.8
2003	33.3
2004	33
2005	32.5
2006	32.1
2007	31.7
2008	31.5
2009	31.1
2010	30.5
2011	30.2
2012	30.1
2013	29.9
2014	29.6
2015	29.5
2016	29.7
2017	30
2018	30.4
2019	30.6