Year	Percent
1992	25.92
1999	20.96
2000	19.86
2001	20.98
2002	20.95
2006	20.25
2007	20.84
2008	19.77
2009	20.43
2012	24.68
2013	23.77
2014	23.03
2015	22.74
2016	24.49