Year	Percent
1987	10.9
1994	13
2002	10.7
2003	14.1
2004	9.9
2005	10
2006	8.3
2007	6.7
2008	6
2009	5
2010	4.5
2011	4.1
2012	3.4
2013	2.9
2014	2.4
2015	2.7
2016	1.8