Year	Ratio
1971-01-01	0.442389994859695
1998-01-01	0.538079977035522
1999-01-01	0.529460012912750
2000-01-01	0.544290006160736
2001-01-01	0.566179990768433
2002-01-01	0.603280007839203
2003-01-01	0.644420027732849
2004-01-01	0.700919985771179
2006-01-01	0.795490026473999
2007-01-01	0.824850022792816
2008-01-01	0.854759991168976