Quarter	Millions of US Dollars
1972-01-01	20
1972-04-01	20
1974-07-01	9
1976-10-01	14
1977-07-01	25
1978-01-01	91
1978-07-01	70
1978-10-01	22
1979-01-01	61
1980-04-01	-20
1980-07-01	25
1982-01-01	-14
1982-07-01	-25
1983-01-01	-9
1984-01-01	-20
1985-10-01	-36
1986-01-01	0
1986-10-01	-12
1987-01-01	-3
1987-07-01	-26
1988-01-01	-92
1990-07-01	-24
1993-01-01	-41
1994-01-01	-112
1996-07-01	3222
1997-01-01	500
1997-07-01	700
1998-04-01	300
1998-10-01	-613
1999-01-01	500
2000-04-01	-26
2000-07-01	350
2001-01-01	750
2001-04-01	-145
2001-07-01	-43
2001-10-01	-354
2002-01-01	-347
2002-07-01	41
2002-10-01	29
2003-01-01	168
2003-07-01	-47
2004-01-01	179
2004-04-01	-24
2004-07-01	-9
2004-10-01	600
2005-07-01	250
2005-10-01	961
2006-01-01	1363
2006-04-01	-610
2006-07-01	-46
2007-04-01	450
2008-04-01	-365
2009-01-01	323
2009-10-01	1000
2011-01-01	79
2012-01-01	-150
2012-07-01	-280
2013-04-01	750
2013-10-01	500
2014-07-01	1250
2015-01-01	-221
2015-10-01	450
2016-01-01	1000
2017-04-01	1422
2018-04-01	1200