Year	%
2006	17.1
2007	16.3
2008	16.9
2009	17
2010	16.7
2011	17.1
2012	16.6
2013	16.7
2014	16.2
2015	16.2
2016	15.5
2017	15.4
2018	14.9
2019	15.2
2020	14.9
2021	15.5