Year	%
2000	32.2
2001	31.9
2002	31.6
2003	31.3
2004	31.1
2005	30.7
2006	30.3
2007	29.9
2008	29.6
2009	29.3
2010	29
2011	28.9
2012	28.8
2013	28.8
2014	28.9
2015	29
2016	29.2
2017	29.3
2018	29.4
2019	29.4