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	0
1976-01-01	0
1976-04-01	0
1976-07-01	0
1976-10-01	0
1977-01-01	0
1977-04-01	0
1977-07-01	30
1977-10-01	98
1978-01-01	127
1978-04-01	154
1978-07-01	134
1978-10-01	82
1979-01-01	157
1979-04-01	294
1979-07-01	378
1979-10-01	525
1980-01-01	413
1980-04-01	280
1980-07-01	208
1980-10-01	70
1981-01-01	118
1981-04-01	182
1981-07-01	434
1981-10-01	455
1982-01-01	421
1982-04-01	372
1982-07-01	258
1982-10-01	438
1983-01-01	472
1983-04-01	521
1983-07-01	570
1983-10-01	439
1984-01-01	418
1984-04-01	357
1984-07-01	233
1984-10-01	882
1985-01-01	961
1985-04-01	1056
1985-07-01	1147
1985-10-01	745
1986-01-01	902
1986-04-01	860
1986-07-01	1045
1986-10-01	1042
1987-01-01	958
1987-04-01	1293
1987-07-01	1649
1987-10-01	1772
1988-01-01	1696
1988-04-01	1492
1988-07-01	1150
1988-10-01	848
1989-01-01	939
1989-04-01	1071
1989-07-01	1008
1989-10-01	1090
1990-01-01	1956
1990-04-01	1583
1990-07-01	1706
1990-10-01	1676
1991-01-01	1075
1991-04-01	1319
1991-07-01	1330
1991-10-01	2025
1992-01-01	2154
1992-04-01	2258
1992-07-01	2840
1992-10-01	2973
1993-01-01	2566
1993-04-01	2594
1993-07-01	4899
1993-10-01	4909
1994-01-01	6484
1994-04-01	6980
1994-07-01	7208
1994-10-01	6038
1995-01-01	3616
1995-04-01	4656
1995-07-01	7016
1995-10-01	9068
1996-01-01	10414
1996-04-01	10558
1996-07-01	8992
1996-10-01	9208
1997-01-01	9559
1997-04-01	10789
1997-07-01	12080
1997-10-01	11349
1998-01-01	12184
1998-04-01	11999
1998-07-01	10006
1998-10-01	12300
1999-01-01	10559
1999-04-01	10599
1999-07-01	10426
1999-10-01	10196
2000-01-01	11417
2000-04-01	12888
2000-07-01	13163
2000-10-01	12188
2001-01-01	13046
2001-04-01	13857
2001-07-01	15655
2001-10-01	16851
2002-01-01	16473
2002-04-01	17576
2002-07-01	16203
2002-10-01	16815
2003-01-01	17761
2003-04-01	21113
2003-07-01	22786
2003-10-01	24069
2004-01-01	23627
2004-04-01	20768
2004-07-01	19980
2004-10-01	17659
2005-01-01	17846
2005-04-01	16223
2005-07-01	15437
2005-10-01	17053
2006-01-01	18581
2006-04-01	20895
2006-07-01	24126
2006-10-01	24052
2007-01-01	22771
2007-04-01	22374
2007-07-01	21238
2007-10-01	22474
2008-01-01	24667
2008-04-01	22819
2008-07-01	21695
2008-10-01	19567
2009-01-01	16601
2009-04-01	14154
2009-07-01	13303
2009-10-01	14512
2010-01-01	19647
2010-04-01	24968
2010-07-01	27561
2010-10-01	26328
2011-01-01	25849
2011-04-01	28883
2011-07-01	27213
2011-10-01	33911
2012-01-01	38014
2012-04-01	35407
2012-07-01	41255
2012-10-01	39610
2013-01-01	33217
2013-04-01	42884
2013-07-01	45354
2013-10-01	47989
2014-01-01	51787
2014-04-01	42544
2014-07-01	33848
2014-10-01	34317
2015-01-01	32969
2015-04-01	36762
2015-07-01	41397
2015-10-01	44505
2016-01-01	48894
2016-04-01	58357
2016-07-01	55173
2016-10-01	55408
2017-01-01	57985
2017-04-01	60351
2017-07-01	64110
2017-10-01	57537
2018-01-01	53263
2018-04-01	50905