Year	Percent
1996	16.2
1997	15.6
1998	15.5
1999	15.6
2000	15.4
2001	15.4
2002	16
2003	16.2
2004	16.5
2005	16.1
2006	16.1
2007	15.8
2008	15.9
2009	15.7
2010	15.5
2011	15.6
2012	15.7
2013	15.6
2014	15.9
2015	15.9
2016	16