Year	Percent
1987	5
1989	4.6
1993	4.1
2004	3.3
2005	2.6
2006	3.4
2007	3.5
2008	3.6
2009	3.6
2010	3.2
2011	3.2
2012	2.9
2013	2.9
2014	2.9
2015	3