Year	%
2000	30.5
2001	31.2
2002	32
2003	32.6
2004	32.7
2005	32.9
2006	32.6
2007	31.3
2008	30.5
2009	30.3
2010	29.7
2011	29.8
2012	28.9
2013	28.7
2014	28.8
2015	29
2016	29.3
2017	29.5
2018	28.9
2019	28.6