Year	Percent
1991	69.5
1996	87.6
1997	98.6
1998	98.6
1999	98.6
2000	98.6
2001	98.3
2002	98.5
2003	98.4
2004	98.6
2005	98.6
2006	97
2007	98.6
2008	98.8
2009	98.9
2010	98.9
2011	99
2012	99
2013	99.1
2014	99.1
2015	99.1