Year	Percent
2006	39.9
2007	35
2008	31.7
2009	31.7
2010	33.7
2011	36.8
2012	38
2013	37
2014	30.6
2015	32.1
2016	25.4
2017	25.6
2018	22.4
2019	20.1
2020	25.3
2021	33.3