Year	Ratio
1971-01-01	0.229240000247955
1972-01-01	0.205550000071526
1973-01-01	0.194440007209778
1976-01-01	0.216539993882179
1977-01-01	0.215079993009567
1978-01-01	0.264149993658066
1979-01-01	0.266909986734390
1980-01-01	0.342570006847382
1981-01-01	0.353069990873337
1982-01-01	0.351419985294342
1986-01-01	0.363359987735748
1987-01-01	0.398779988288879
1988-01-01	0.379260003566742
1989-01-01	0.405019998550415
1990-01-01	0.397139996290207
1991-01-01	0.409839987754822
1992-01-01	0.409520000219345
2001-01-01	0.521499991416931
2009-01-01	0.557269990444183
2011-01-01	0.550620019435883
2012-01-01	0.513469994068146
2016-01-01	0.637839972972870