Quarter	Millions of US Dollars
1968-01-01	0
1968-04-01	0
1968-07-01	0
1968-10-01	0
1969-01-01	0
1969-04-01	0
1969-07-01	0
1969-10-01	0
1970-01-01	0
1970-04-01	0
1970-07-01	0
1970-10-01	0
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	0
1977-10-01	25
1978-01-01	59
1978-04-01	117
1978-07-01	162
1978-10-01	150
1979-01-01	121
1979-04-01	90
1979-07-01	70
1979-10-01	90
1980-01-01	79
1980-04-01	118
1980-07-01	115
1980-10-01	65
1981-01-01	182
1981-04-01	329
1981-07-01	378
1981-10-01	442
1982-01-01	440
1982-04-01	384
1982-07-01	426
1982-10-01	463
1983-01-01	330
1983-04-01	170
1983-07-01	151
1983-10-01	113
1984-01-01	124
1984-04-01	175
1984-07-01	233
1984-10-01	420
1985-01-01	449
1985-04-01	519
1985-07-01	425
1985-10-01	362
1986-01-01	594
1986-04-01	973
1986-07-01	1082
1986-10-01	1521
1987-01-01	1487
1987-04-01	1273
1987-07-01	1516
1987-10-01	1639
1988-01-01	2039
1988-04-01	2080
1988-07-01	2352
1988-10-01	2398
1989-01-01	2476
1989-04-01	3169
1989-07-01	3546
1989-10-01	3781
1990-01-01	4122
1990-04-01	4596
1990-07-01	4997
1990-10-01	5607
1991-01-01	6681
1991-04-01	6843
1991-07-01	7431
1991-10-01	7209
1992-01-01	8289
1992-04-01	9730
1992-07-01	11357
1992-10-01	12077
1993-01-01	12867
1993-04-01	12067
1993-07-01	14823
1993-10-01	15664
1994-01-01	15929
1994-04-01	17560
1994-07-01	19281
1994-10-01	19947
1995-01-01	22157
1995-04-01	26018
1995-07-01	27466
1995-10-01	32285
1996-01-01	35908
1996-04-01	37443
1996-07-01	35455
1996-10-01	43867
1997-01-01	46289
1997-04-01	52972
1997-07-01	55848
1997-10-01	64981
1998-01-01	69049
1998-04-01	69130
1998-07-01	71665
1998-10-01	73920
1999-01-01	86354
1999-04-01	90238
1999-07-01	113349
1999-10-01	132469
2000-01-01	145844
2000-04-01	169819
2000-07-01	174861
2000-10-01	190961
2001-01-01	187905
2001-04-01	185687
2001-07-01	184689
2001-10-01	186215
2002-01-01	204374
2002-04-01	232029
2002-07-01	248454
2002-10-01	250768
2003-01-01	287877
2003-04-01	283200
2003-07-01	258641
2003-10-01	300375
2004-01-01	284377
2004-04-01	306265
2004-07-01	325114
2004-10-01	350814
2005-01-01	336332
2005-04-01	300416
2005-07-01	287089
2005-10-01	283817
2006-01-01	306976
2006-04-01	334814
2006-07-01	348318
2006-10-01	361407
2007-01-01	404359
2007-04-01	443884
2007-07-01	456377
2007-10-01	483220
2008-01-01	511366
2008-04-01	510073
2008-07-01	490027
2008-10-01	463752
2009-01-01	406092
2009-04-01	436193
2009-07-01	417963
2009-10-01	410666
2010-01-01	417305
2010-04-01	388258
2010-07-01	419828
2010-10-01	382444
2011-01-01	404045
2011-04-01	408554
2011-07-01	429087
2011-10-01	451309
2012-01-01	457052
2012-04-01	470509
2012-07-01	463842
2012-10-01	458292
2013-01-01	460836
2013-04-01	468115
2013-07-01	455406
2013-10-01	440889
2014-01-01	446296
2014-04-01	456572
2014-07-01	460382
2014-10-01	503406
2015-01-01	470245
2015-04-01	476687
2015-07-01	472130
2015-10-01	419539
2016-01-01	454100
2016-04-01	434107
2016-07-01	454196
2016-10-01	429757
2017-01-01	406026
2017-04-01	431569
2017-07-01	439494
2017-10-01	419459
2018-01-01	443124
2018-04-01	399309