Year	Percent
1970	0.90522
1971	0.9038
1972	0.89456
1973	0.90155
1974	0.91767
1975	0.92969
1976	0.94085
1977	0.95458
1998	0.96243
1999	0.96123
2000	0.95509
2001	0.96405
2002	0.95153
2003	0.96375
2004	0.94562
2005	0.9523
2006	0.95034
2007	0.92032
2009	0.9381
2010	0.93306
2011	0.91194
2012	0.92453
2013	0.92832
2014	0.93362
2015	0.93547