Year	%
2004	16.4
2005	16.5
2006	16.5
2007	16.4
2008	16.2
2009	16.4
2010	17.6
2011	17.2
2012	16.6
2013	16.3
2014	16
2015	15.9
2016	15.8
2017	15.9
2018	16.3
2019	16.1
2020	15.7
2021	15.6