Year	%
2000	28.7
2001	27.7
2002	26.9
2003	26.1
2004	25.3
2005	24.4
2006	23.5
2007	22.6
2008	21.8
2009	21
2010	20.2
2011	19.7
2012	19.3
2013	19.1
2014	18.9
2015	18.9
2016	19
2017	18.8
2018	18.6
2019	18.5