Year	%
2000	21.3
2001	21.3
2002	21.3
2003	21.2
2004	21.3
2005	21.4
2006	19
2007	18.2
2008	18.2
2009	18
2010	17.6
2011	17.7
2012	17.9
2013	17.7
2014	17.2
2015	17.1
2016	17.2
2017	17.8
2018	23.4
2019	23.2