Year	Percent
1971	0.92484
1972	0.93868
1973	0.94155
1974	0.94947
1975	0.96537
1976	0.96453
1977	0.96454
1978	0.97141
1979	0.98524
1980	0.88597
1986	1.00657
1988	0.95997
1990	0.97082
1991	1.02762
1993	1.04079
1994	1.01678
1995	1.01538
1996	1.02122
1998	1.0169
1999	1.0186
2000	1.01097
2001	1.01969
2002	1.0054
2003	1.01755
2004	1.01962
2005	1.01925
2006	1.01336
2007	1.00511
2008	0.99775
2009	1.00307
2010	0.99844
2011	0.99472
2012	0.98528
2013	0.97589
2014	0.96818
2015	0.96687
2016	0.97001