Year	%
2004	36.4
2005	39
2006	35.6
2007	37.5
2008	37.2
2009	36
2010	35
2011	35.8
2012	35.2
2013	35.5
2014	35.1
2015	34.2
2016	34.3
2017	35.6
2018	35.1
2019	34.5
2020	35.7
2021	34.3