Year	%
2000	27.6
2001	27
2002	26.8
2003	27.1
2004	26.5
2005	25.3
2006	25.4
2007	25.6
2008	24.1
2009	23.8
2010	23.4
2011	23.4
2012	23.2
2013	22.3
2014	22
2015	21.8
2016	22.8
2017	20.5
2018	21.4
2019	20.6