Year	Ratio
1971-01-01	0.256009995937347
1980-01-01	0.361519992351532
1981-01-01	0.387300014495850
1982-01-01	0.387050002813339
1983-01-01	0.374179989099503
1984-01-01	0.384609997272491
1985-01-01	0.364609986543655
1986-01-01	0.356339991092682
1987-01-01	0.334329992532730
1989-01-01	0.325150012969971
1990-01-01	0.322499990463257
1991-01-01	0.319849997758865
1993-01-01	0.327659994363785
1994-01-01	0.326759994029999
1996-01-01	0.343930006027222
1999-01-01	0.352730005979538
2001-01-01	0.390650004148483
2002-01-01	0.409009993076324
2003-01-01	0.451359987258911
2004-01-01	0.449730008840561
2005-01-01	0.497979998588562
2006-01-01	0.523479998111725
2008-01-01	0.577629983425140
2011-01-01	0.631489992141724
2014-01-01	0.656109988689423