Year	Percent
2005	18.6
2006	16.3
2007	16.7
2008	17.1
2009	16.9
2010	16.1
2011	16.3
2012	15
2013	15
2014	14.7
2015	14.3
2016	13.5
2017	13.9
2018	14.4
2019	15
2020	14.4