Year	%
2004	22.1
2005	24.9
2006	21.8
2007	20.8
2008	21.4
2009	21.8
2010	21.9
2011	21
2012	20.5
2013	22.2
2014	20.3
2015	20.9
2016	19.9
2017	18.4
2018	19.6
2019	18.8
2020	19.1
2021	19.2