Year	Percent
2004	48.94
2005	49.1
2006	50.16
2007	49.74
2008	48.68
2009	50.7
2010	52.01
2011	51.98
2012	52.58
2013	52.85
2014	55.48
2015	56.06
2016	56.96
2017	57.48