Year	%
2000	31.6
2001	31.8
2002	31.8
2003	31.9
2004	31.8
2005	31.6
2006	31.2
2007	30.7
2008	30.1
2009	29.5
2010	29
2011	28.5
2012	28.1
2013	27.8
2014	27.6
2015	27.4
2016	27.2
2017	27.1
2018	27.1
2019	27.1