Year	Percent
1987	2.4
1994	2.3
2002	2.3
2003	2.1
2004	2
2005	1.9
2006	2.1
2007	2.1
2008	2.1
2009	2.2
2010	2.2
2011	2.2
2012	2.2
2013	2.2
2014	2.2
2015	2.1
2016	2.2