Year	%
2000	22.7
2001	22.4
2002	23
2003	22.7
2004	22.8
2005	22.2
2006	21.5
2007	21.1
2008	20.2
2009	19.6
2010	18.9
2011	18.7
2012	18.6
2013	18.4
2014	18.1
2015	18
2016	17.8
2017	17.7
2018	17.7
2019	18.1