Year	Percent
1986	52.4
1989	55.5
1992	56.5
1996	52.7
1997	53.7
2000	56.6
2001	55.6
2002	54.6
2003	57
2004	57.1
2005	55.2
2006	56.9
2007	54.1
2008	53.4
2009	54.2
2010	52.5
2011	52.9
2012	51.5
2013	53
2014	50
2015	50.6
2016	51.1