Year	%
2000	28.9
2001	28.6
2002	28.6
2003	28.7
2004	29
2005	29.4
2006	29.7
2007	29.9
2008	30.7
2009	31.6
2010	32.3
2011	32.8
2012	33.3
2013	33.1
2014	32.4
2015	31.8
2016	31.3
2017	30.9
2018	30.8
2019	30.6