Year	Percent
1996	16.1
2001	16.1
2002	16.1
2003	16.4
2004	16.6
2005	15.2
2006	16.6
2007	16.7
2008	16.9
2009	17.1
2010	17.1
2011	17.1
2012	17.1
2013	17.3
2014	17.3
2015	17.2