Year	Percent
1987	11.4
1989	10.4
1993	9.7
2004	8.3
2005	7.1
2006	8.7
2007	8.7
2008	8.8
2009	8.9
2010	8.2
2011	8.1
2012	7.6
2013	7.6
2014	7.6
2015	7.8