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	0
1975-07-01	0
1975-10-01	23
1976-01-01	24
1976-04-01	24
1976-07-01	25
1976-10-01	0
1977-01-01	0
1977-04-01	4
1977-07-01	11
1977-10-01	12
1978-01-01	41
1978-04-01	44
1978-07-01	39
1978-10-01	40
1979-01-01	144
1979-04-01	288
1979-07-01	343
1979-10-01	403
1980-01-01	420
1980-04-01	652
1980-07-01	659
1980-10-01	884
1981-01-01	757
1981-04-01	455
1981-07-01	557
1981-10-01	538
1982-01-01	664
1982-04-01	934
1982-07-01	946
1982-10-01	765
1983-01-01	725
1983-04-01	494
1983-07-01	357
1983-10-01	461
1984-01-01	395
1984-04-01	737
1984-07-01	1235
1984-10-01	2425
1985-01-01	2871
1985-04-01	2613
1985-07-01	2821
1985-10-01	1819
1986-01-01	1985
1986-04-01	2211
1986-07-01	2305
1986-10-01	2460
1987-01-01	2197
1987-04-01	1749
1987-07-01	2029
1987-10-01	2391
1988-01-01	2232
1988-04-01	2135
1988-07-01	1404
1988-10-01	1249
1989-01-01	1383
1989-04-01	1727
1989-07-01	1920
1989-10-01	2753
1990-01-01	2563
1990-04-01	2988
1990-07-01	2925
1990-10-01	2404
1991-01-01	2037
1991-04-01	2080
1991-07-01	2901
1991-10-01	3252
1992-01-01	3905
1992-04-01	4873
1992-07-01	5154
1992-10-01	4822
1993-01-01	4993
1993-04-01	3822
1993-07-01	6811
1993-10-01	5664
1994-01-01	4995
1994-04-01	4528
1994-07-01	4289
1994-10-01	5356
1995-01-01	5005
1995-04-01	6018
1995-07-01	5139
1995-10-01	4873
1996-01-01	5460
1996-04-01	5652
1996-07-01	3879
1996-10-01	5164
1997-01-01	5545
1997-04-01	5549
1997-07-01	6538
1997-10-01	5949
1998-01-01	7144
1998-04-01	6947
1998-07-01	7852
1998-10-01	9852
1999-01-01	9860
1999-04-01	11219
1999-07-01	12139
1999-10-01	9490
2000-01-01	9632
2000-04-01	9565
2000-07-01	9641
2000-10-01	14470
2001-01-01	25310
2001-04-01	23738
2001-07-01	26104
2001-10-01	22118
2002-01-01	17109
2002-04-01	21140
2002-07-01	27216
2002-10-01	30813
2003-01-01	36448
2003-04-01	37764
2003-07-01	34877
2003-10-01	35697
2004-01-01	27914
2004-04-01	30153
2004-07-01	29507
2004-10-01	32913
2005-01-01	23999
2005-04-01	21599
2005-07-01	24574
2005-10-01	24848
2006-01-01	26658
2006-04-01	29235
2006-07-01	26407
2006-10-01	27716
2007-01-01	31196
2007-04-01	31574
2007-07-01	31615
2007-10-01	34727
2008-01-01	43821
2008-04-01	40480
2008-07-01	36670
2008-10-01	32388
2009-01-01	22484
2009-04-01	31689
2009-07-01	33382
2009-10-01	36964
2010-01-01	38265
2010-04-01	37483
2010-07-01	39970
2010-10-01	34393
2011-01-01	42943
2011-04-01	40428
2011-07-01	34061
2011-10-01	34019
2012-01-01	34510
2012-04-01	43374
2012-07-01	49646
2012-10-01	52449
2013-01-01	55017
2013-04-01	51117
2013-07-01	59991
2013-10-01	68888
2014-01-01	68152
2014-04-01	70643
2014-07-01	58958
2014-10-01	47421
2015-01-01	41881
2015-04-01	40533
2015-07-01	43675
2015-10-01	46093
2016-01-01	53277
2016-04-01	51394
2016-07-01	49258
2016-10-01	50593
2017-01-01	41916
2017-04-01	40040
2017-07-01	45369
2017-10-01	48526
2018-01-01	56129
2018-04-01	53421