Year	%
2006	39.6
2007	37.5
2008	36.4
2009	35.6
2010	35.5
2011	35.9
2012	36.5
2013	36.9
2014	36
2015	35.9
2016	34.4
2017	36
2018	35.8
2019	34.8
2020	34.6
2021	33.9