Year	Percent
1970	0.92987
1971	0.93285
1972	0.94203
1973	0.93962
1975	0.94654
1976	0.94578
1977	0.94658
1978	0.94952
1986	0.95742
1987	0.95964
1988	0.96156
1989	0.97849
1990	0.97556
1991	0.98128
1993	0.98397
1994	0.98308
1995	0.99187
1996	0.99047
1997	0.99263
1998	0.98966
1999	0.98503
2000	0.98454
2001	0.98275
2002	0.98109
2003	0.98257
2004	0.98672
2005	0.99095
2006	0.99423
2007	0.99466
2008	0.99774
2009	0.99973
2010	0.99803
2011	1.00161
2012	1.00932