Year	Percent
1996	42.3
2001	42.9
2002	42.4
2003	41.4
2004	40.3
2005	46.2
2006	39.5
2007	39.3
2008	38.2
2009	37.8
2010	37.7
2011	37.6
2012	37.7
2013	36.9
2014	37
2015	36.9