Year	%
2006	20.1
2007	18.4
2008	17
2009	16.8
2010	17.9
2011	18.2
2012	18.9
2013	20.9
2014	21.3
2015	20.5
2016	18.8
2017	19.2
2018	18.1
2019	18
2020	18
2021	17