Year	%
2004	22.3
2005	22
2006	21.6
2007	21.9
2008	21.6
2009	21.9
2010	21.8
2011	21.6
2012	21.4
2013	20.7
2014	21.3
2015	21.7
2016	21.7
2017	21.9
2018	21.4
2019	21.8
2020	21.6
2021	21.8