Year	Ratio
1970-01-01	0.234380006790161
1971-01-01	0.260930001735687
1972-01-01	0.279839992523193
1973-01-01	0.292600005865097
1974-01-01	0.280059993267059
1975-01-01	0.304960012435913
1976-01-01	0.328150004148483
1977-01-01	0.343760013580322
1978-01-01	0.376610010862350
2002-01-01	0.741410017013550
2007-01-01	1.030339956283570
2013-01-01	1.050709962844850
2014-01-01	1.120290040969850
2015-01-01	1.180580019950870