Quarter	Billions of US Dollars
1973-10-01	0.02500
1997-01-01	0.22500
2004-04-01	0.25000
2006-10-01	0.95000
2007-04-01	0.01500
2012-01-01	0.02600
2012-10-01	0.02597
2013-01-01	0.50000
2014-07-01	0.50000
2014-10-01	0.50000
2015-04-01	1.30000