Year	%
2006	36.7
2007	37.5
2008	37.5
2009	38.6
2010	37.6
2011	37.8
2012	38
2013	37.8
2014	37.8
2015	38.1
2016	37.9
2017	38
2018	37.5
2019	39.4
2020	39.7