Year	%
2000	31.6
2001	31.7
2002	31.1
2003	30.8
2004	30.5
2005	30.4
2006	30.2
2007	29.7
2008	29.4
2009	28.8
2010	28.3
2011	27.8
2012	27.4
2013	27.1
2014	26.9
2015	26.8
2016	26.7
2017	26.7
2018	26.8
2019	26.8