Year	Percent
1990	47.1
1995	61.8
1997	58.4
1999	58.6
2001	58.9
2002	61.1
2003	59.4
2004	57.3
2005	56.3
2006	57.6
2007	57.6
2008	55.7
2009	53.9
2010	55.6
2011	56.7
2012	52.5
2013	53.1
2014	55.6
2015	52.7
2016	53.1