Year	Percent
1971	0.75371
1998	0.95276
1999	0.95601
2000	0.95346
2001	0.95575
2002	0.95796
2003	0.96165
2004	0.9649
2005	0.96978
2006	0.97442
2007	0.97843
2008	0.98013
2009	0.98234
2010	0.98307
2011	0.98568
2012	0.98562
2013	0.98113
2014	0.97892
2015	0.97742
2016	0.97832