Year	%
2000	36.3
2001	35.9
2002	35.4
2003	34.9
2004	34.3
2005	33.5
2006	32.6
2007	31.7
2008	31
2009	30.5
2010	30.1
2011	29.8
2012	29.4
2013	29.1
2014	29
2015	28.7
2016	28.3
2017	27.9
2018	27.7
2019	27.5