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	10
1976-04-01	10
1976-07-01	10
1976-10-01	10
1977-01-01	0
1977-04-01	0
1977-07-01	0
1977-10-01	0
1978-01-01	0
1978-04-01	0
1978-07-01	14
1978-10-01	83
1979-01-01	134
1979-04-01	201
1979-07-01	368
1979-10-01	751
1980-01-01	973
1980-04-01	1310
1980-07-01	1271
1980-10-01	886
1981-01-01	1077
1981-04-01	1133
1981-07-01	1107
1981-10-01	1438
1982-01-01	1347
1982-04-01	1390
1982-07-01	1287
1982-10-01	1330
1983-01-01	982
1983-04-01	811
1983-07-01	948
1983-10-01	658
1984-01-01	782
1984-04-01	613
1984-07-01	512
1984-10-01	1563
1985-01-01	1535
1985-04-01	1460
1985-07-01	1785
1985-10-01	1009
1986-01-01	1151
1986-04-01	1649
1986-07-01	2062
1986-10-01	2067
1987-01-01	2369
1987-04-01	2026
1987-07-01	1535
1987-10-01	1719
1988-01-01	1221
1988-04-01	1028
1988-07-01	1267
1988-10-01	936
1989-01-01	1425
1989-04-01	1726
1989-07-01	2023
1989-10-01	2316
1990-01-01	2638
1990-04-01	2799
1990-07-01	3067
1990-10-01	3747
1991-01-01	3743
1991-04-01	3982
1991-07-01	3829
1991-10-01	3600
1992-01-01	3529
1992-04-01	4517
1992-07-01	4638
1992-10-01	3946
1993-01-01	3748
1993-04-01	2749
1993-07-01	2651
1993-10-01	2544
1994-01-01	2427
1994-04-01	3046
1994-07-01	3386
1994-10-01	2906
1995-01-01	3630
1995-04-01	3037
1995-07-01	4213
1995-10-01	4513
1996-01-01	6686
1996-04-01	7686
1996-07-01	5494
1996-10-01	4451
1997-01-01	4723
1997-04-01	5174
1997-07-01	4943
1997-10-01	4360
1998-01-01	4911
1998-04-01	4210
1998-07-01	4900
1998-10-01	4347
1999-01-01	4355
1999-04-01	4222
1999-07-01	5886
1999-10-01	3978
2000-01-01	6070
2000-04-01	7393
2000-07-01	7987
2000-10-01	7283
2001-01-01	7251
2001-04-01	6218
2001-07-01	6237
2001-10-01	6093
2002-01-01	7025
2002-04-01	10024
2002-07-01	8693
2002-10-01	8048
2003-01-01	8386
2003-04-01	7694
2003-07-01	7610
2003-10-01	9463
2004-01-01	9076
2004-04-01	8826
2004-07-01	9068
2004-10-01	11769
2005-01-01	10770
2005-04-01	12001
2005-07-01	10736
2005-10-01	10688
2006-01-01	14333
2006-04-01	17741
2006-07-01	19274
2006-10-01	20098
2007-01-01	22292
2007-04-01	21389
2007-07-01	23365
2007-10-01	29655
2008-01-01	37966
2008-04-01	34567
2008-07-01	32885
2008-10-01	36026
2009-01-01	35520
2009-04-01	34452
2009-07-01	37701
2009-10-01	32862
2010-01-01	34357
2010-04-01	35449
2010-07-01	35137
2010-10-01	33752
2011-01-01	39409
2011-04-01	36025
2011-07-01	34849
2011-10-01	36992
2012-01-01	43652
2012-04-01	44951
2012-07-01	48660
2012-10-01	42855
2013-01-01	36356
2013-04-01	35929
2013-07-01	36315
2013-10-01	43490
2014-01-01	42254
2014-04-01	42541
2014-07-01	42962
2014-10-01	37554
2015-01-01	40466
2015-04-01	33464
2015-07-01	32546
2015-10-01	35848
2016-01-01	32262
2016-04-01	38852
2016-07-01	40941
2016-10-01	33490
2017-01-01	37520
2017-04-01	34766
2017-07-01	29272
2017-10-01	29086
2018-01-01	28706
2018-04-01	27132