Year	%
2006	22.9
2007	22.3
2008	22.6
2009	22.8
2010	22.7
2011	22.7
2012	22.4
2013	22.6
2014	22.1
2015	22.6
2016	21.8
2017	21.3
2018	21
2019	21.4
2020	20.7
2021	21.9