Quarter	Millions of US Dollars
1971-01-01	0
1971-04-01	0
1971-07-01	0
1971-10-01	0
1972-01-01	0
1972-04-01	0
1972-07-01	0
1972-10-01	0
1973-01-01	0
1973-04-01	0
1973-07-01	0
1973-10-01	0
1974-01-01	0
1974-04-01	0
1974-07-01	0
1974-10-01	0
1975-01-01	0
1975-04-01	8
1975-07-01	8
1975-10-01	8
1976-01-01	8
1976-04-01	8
1976-07-01	8
1976-10-01	8
1977-01-01	8
1977-04-01	0
1977-07-01	0
1977-10-01	0
1978-01-01	0
1978-04-01	0
1978-07-01	0
1978-10-01	0
1979-01-01	0
1979-04-01	0
1979-07-01	0
1979-10-01	31
1980-01-01	27
1980-04-01	31
1980-07-01	111
1980-10-01	87
1981-01-01	84
1981-04-01	82
1981-07-01	8
1981-10-01	0
1982-01-01	0
1982-04-01	0
1982-07-01	24
1982-10-01	140
1983-01-01	160
1983-04-01	259
1983-07-01	574
1983-10-01	467
1984-01-01	474
1984-04-01	396
1984-07-01	111
1984-10-01	94
1985-01-01	104
1985-04-01	165
1985-07-01	176
1985-10-01	277
1986-01-01	666
1986-04-01	955
1986-07-01	1447
1986-10-01	2133
1987-01-01	2345
1987-04-01	2030
1987-07-01	1743
1987-10-01	972
1988-01-01	731
1988-04-01	999
1988-07-01	1161
1988-10-01	1561
1989-01-01	1095
1989-04-01	740
1989-07-01	586
1989-10-01	345
1990-01-01	1224
1990-04-01	1551
1990-07-01	1758
1990-10-01	2266
1991-01-01	1695
1991-04-01	1488
1991-07-01	1604
1991-10-01	1824
1992-01-01	1991
1992-04-01	2318
1992-07-01	2330
1992-10-01	1872
1993-01-01	1441
1993-04-01	1725
1993-07-01	3032
1993-10-01	2669
1994-01-01	2786
1994-04-01	2226
1994-07-01	2346
1994-10-01	2355
1995-01-01	5040
1995-04-01	5675
1995-07-01	6280
1995-10-01	5941
1996-01-01	4704
1996-04-01	4343
1996-07-01	2082
1996-10-01	2223
1997-01-01	2066
1997-04-01	3074
1997-07-01	3889
1997-10-01	3947
1998-01-01	3355
1998-04-01	2409
1998-07-01	1954
1998-10-01	3636
1999-01-01	4179
1999-04-01	4181
1999-07-01	5127
1999-10-01	3259
2000-01-01	2977
2000-04-01	4147
2000-07-01	7566
2000-10-01	4979
2001-01-01	8922
2001-04-01	9169
2001-07-01	8482
2001-10-01	7155
2002-01-01	6222
2002-04-01	5644
2002-07-01	4739
2002-10-01	5941
2003-01-01	6655
2003-04-01	6585
2003-07-01	6255
2003-10-01	5123
2004-01-01	5596
2004-04-01	4989
2004-07-01	7084
2004-10-01	7233
2005-01-01	7419
2005-04-01	5688
2005-07-01	12150
2005-10-01	10721
2006-01-01	11256
2006-04-01	12146
2006-07-01	8826
2006-10-01	12669
2007-01-01	14892
2007-04-01	15436
2007-07-01	14821
2007-10-01	15124
2008-01-01	12252
2008-04-01	10438
2008-07-01	7483
2008-10-01	6118
2009-01-01	5450
2009-04-01	12364
2009-07-01	10496
2009-10-01	13047
2010-01-01	10999
2010-04-01	7204
2010-07-01	14494
2010-10-01	13032
2011-01-01	24369
2011-04-01	23727
2011-07-01	24451
2011-10-01	21561
2012-01-01	20805
2012-04-01	17696
2012-07-01	11491
2012-10-01	11747
2013-01-01	12119
2013-04-01	16800
2013-07-01	17146
2013-10-01	19612
2014-01-01	12332
2014-04-01	10684
2014-07-01	10100
2014-10-01	9330
2015-01-01	12031
2015-04-01	12083
2015-07-01	11584
2015-10-01	12908
2016-01-01	10339
2016-04-01	10182
2016-07-01	10666
2016-10-01	10811
2017-01-01	14606
2017-04-01	16097
2017-07-01	16279
2017-10-01	16581
2018-01-01	10930
2018-04-01	7963