Year	Percent
1987	14
1994	14.9
2002	14.8
2003	14.6
2004	15.2
2005	14.8
2006	15.7
2007	15.8
2008	15.9
2009	15.6
2010	15.6
2011	15.2
2012	15.1
2013	15.1
2014	14.7
2015	14.2
2016	14.5