Year	%
2006	19.4
2007	19.7
2008	18.8
2009	19.8
2010	19
2011	18.4
2012	17.8
2013	18.1
2014	17.8
2015	18.2
2016	17.5
2017	17.1
2018	16.9
2019	17.4
2020	18
2021	17.3
2022	17.8