Year	Ratio
1971-01-01	0.599370002746582
1972-01-01	0.665239989757538
1973-01-01	0.745890021324158
1974-01-01	0.819809973239899
1975-01-01	0.855549991130829
1976-01-01	0.880089998245239
1977-01-01	0.908259987831116
1978-01-01	0.918510019779205
1979-01-01	0.918309986591339
1980-01-01	0.920799970626831
1981-01-01	0.933860003948212
1983-01-01	0.933009982109070
1986-01-01	0.942420005798340
1999-01-01	0.985939979553223
2001-01-01	1.017770051956180
2002-01-01	1.001500010490420
2003-01-01	0.970070004463196
2004-01-01	0.972190022468567
2005-01-01	0.989250004291534
2006-01-01	0.959439992904663