Year	Percent
2002	22.4
2004	17.8
2005	18.19
2006	16.12
2007	15.92
2008	16.83
2009	16.98
2010	20.67
2011	20.66
2012	20.48
2013	19.77
2014	19.73
2015	19.47
2016	20.74
2017	19.89