Year	%
2000	23.4
2001	22.1
2002	21.9
2003	20.7
2004	20.2
2005	19.5
2006	19.3
2007	18.5
2008	17.7
2009	16.9
2010	17.9
2011	18.5
2012	18.8
2013	19.3
2014	19.4
2015	19.4
2016	19.2
2017	19.3
2018	18.4
2019	18.4