Year	%
2004	38.4
2005	42.2
2006	37.1
2007	36.7
2008	36.4
2009	35.9
2010	37.7
2011	37.6
2012	38.6
2013	39.4
2014	38.7
2015	38.4
2016	38.4
2017	38.5
2018	37.8
2019	37.8
2020	37.8
2021	38.1