Year	Ratio
1971-01-01	0.947780013084412
1972-01-01	0.957650005817413
1973-01-01	0.960829973220825
1974-01-01	0.960439980030060
1975-01-01	0.962700009346008
1976-01-01	0.974500000476837
1977-01-01	0.973940014839172
1978-01-01	0.978640019893646
1979-01-01	0.982339978218079
1980-01-01	0.979910016059875
1981-01-01	0.977469980716705
1982-01-01	0.992429971694946
1983-01-01	0.995970010757446
1984-01-01	0.995410025119781
1985-01-01	0.994199991226196
1986-01-01	0.990859985351563
1987-01-01	0.983389973640442
1988-01-01	0.990390002727509
1995-01-01	1.014750003814700
1996-01-01	0.999090015888214
1998-01-01	0.996179997920990
2012-01-01	0.985099971294403
2013-01-01	0.980400025844574
2014-01-01	0.978720009326935
2015-01-01	0.976870000362396
2016-01-01	0.978529989719391