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	10
1976-10-01	10
1977-01-01	10
1977-04-01	10
1977-07-01	0
1977-10-01	0
1978-01-01	28
1978-04-01	54
1978-07-01	61
1978-10-01	61
1979-01-01	30
1979-04-01	105
1979-07-01	220
1979-10-01	221
1980-01-01	238
1980-04-01	190
1980-07-01	75
1980-10-01	154
1981-01-01	603
1981-04-01	650
1981-07-01	808
1981-10-01	767
1982-01-01	339
1982-04-01	503
1982-07-01	576
1982-10-01	887
1983-01-01	808
1983-04-01	593
1983-07-01	513
1983-10-01	338
1984-01-01	369
1984-04-01	374
1984-07-01	514
1984-10-01	932
1985-01-01	1205
1985-04-01	1842
1985-07-01	1896
1985-10-01	1849
1986-01-01	1871
1986-04-01	1386
1986-07-01	1468
1986-10-01	1339
1987-01-01	1675
1987-04-01	1847
1987-07-01	1725
1987-10-01	2026
1988-01-01	1978
1988-04-01	2207
1988-07-01	2260
1988-10-01	3038
1989-01-01	2875
1989-04-01	2682
1989-07-01	3499
1989-10-01	3806
1990-01-01	4232
1990-04-01	5671
1990-07-01	5640
1990-10-01	6240
1991-01-01	6567
1991-04-01	6774
1991-07-01	8512
1991-10-01	8076
1992-01-01	8307
1992-04-01	7588
1992-07-01	7296
1992-10-01	7535
1993-01-01	7745
1993-04-01	7172
1993-07-01	25638
1993-10-01	23363
1994-01-01	23232
1994-04-01	20839
1994-07-01	17844
1994-10-01	18325
1995-01-01	19932
1995-04-01	21066
1995-07-01	22972
1995-10-01	22841
1996-01-01	22502
1996-04-01	20451
1996-07-01	17099
1996-10-01	26905
1997-01-01	27228
1997-04-01	29542
1997-07-01	28214
1997-10-01	23836
1998-01-01	25275
1998-04-01	22689
1998-07-01	24487
1998-10-01	23567
1999-01-01	24107
1999-04-01	20985
1999-07-01	23039
1999-10-01	25040
2000-01-01	27831
2000-04-01	25830
2000-07-01	28006
2000-10-01	31090
2001-01-01	28584
2001-04-01	28439
2001-07-01	30241
2001-10-01	27531
2002-01-01	32639
2002-04-01	34081
2002-07-01	35996
2002-10-01	39582
2003-01-01	38113
2003-04-01	41715
2003-07-01	45763
2003-10-01	50215
2004-01-01	50631
2004-04-01	47378
2004-07-01	55015
2004-10-01	59529
2005-01-01	58425
2005-04-01	63771
2005-07-01	60648
2005-10-01	65560
2006-01-01	73887
2006-04-01	84442
2006-07-01	85533
2006-10-01	91174
2007-01-01	88054
2007-04-01	102204
2007-07-01	109210
2007-10-01	106170
2008-01-01	150135
2008-04-01	131319
2008-07-01	124076
2008-10-01	97006
2009-01-01	77202
2009-04-01	85756
2009-07-01	76087
2009-10-01	86332
2010-01-01	85572
2010-04-01	97795
2010-07-01	101198
2010-10-01	104097
2011-01-01	106559
2011-04-01	109636
2011-07-01	106070
2011-10-01	111055
2012-01-01	99245
2012-04-01	98192
2012-07-01	101638
2012-10-01	101441
2013-01-01	104195
2013-04-01	95554
2013-07-01	111586
2013-10-01	117911
2014-01-01	114181
2014-04-01	112119
2014-07-01	107753
2014-10-01	98040
2015-01-01	89425
2015-04-01	89019
2015-07-01	75277
2015-10-01	97688
2016-01-01	117483
2016-04-01	117403
2016-07-01	122484
2016-10-01	107026
2017-01-01	93447
2017-04-01	94732
2017-07-01	79789
2017-10-01	73391
2018-01-01	75940
2018-04-01	69804