Year	Percent
1989	99.9
1990	99.8
1991	99.9
1992	99.7
1993	98.9
1994	99
1995	99.1
1996	99
1997	98.3
1998	99
1999	98
2000	99
2001	99
2002	99.1
2003	99.2
2004	98.9
2005	98.1
2006	98.2
2007	98.8
2008	99.4
2009	99.5
2010	99.5
2011	99.4
2012	99.5
2013	98.5
2014	98.5
2015	95.2