Year	Percent
1992	40.5
1996	45.6
1999	46.9
2000	47
2001	45.8
2002	44.8
2003	42.4
2004	44.2
2005	42.8
2008	43.7
2009	43.1
2010	43.5
2011	42.4
2012	41.4
2013	41.6
2014	41.6
2015	40
2016	40