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	68
1979-01-01	186
1979-04-01	253
1979-07-01	424
1979-10-01	823
1980-01-01	973
1980-04-01	1310
1980-07-01	1271
1980-10-01	926
1981-01-01	1117
1981-04-01	1173
1981-07-01	1147
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	1556
1985-04-01	1481
1985-07-01	1802
1985-10-01	985
1986-01-01	1171
1986-04-01	1649
1986-07-01	2062
1986-10-01	2107
1987-01-01	2384
1987-04-01	2060
1987-07-01	1602
1987-10-01	1812
1988-01-01	1276
1988-04-01	1086
1988-07-01	1398
1988-10-01	1044
1989-01-01	1552
1989-04-01	1853
1989-07-01	2066
1989-10-01	2705
1990-01-01	2769
1990-04-01	2941
1990-07-01	3186
1990-10-01	3866
1991-01-01	4359
1991-04-01	4617
1991-07-01	4518
1991-10-01	4336
1992-01-01	3741
1992-04-01	5071
1992-07-01	5232
1992-10-01	4551
1993-01-01	4205
1993-04-01	2919
1993-07-01	2938
1993-10-01	2761
1994-01-01	2679
1994-04-01	3289
1994-07-01	3470
1994-10-01	3005
1995-01-01	3705
1995-04-01	3137
1995-07-01	4313
1995-10-01	4613
1996-01-01	6816
1996-04-01	7716
1996-07-01	5524
1996-10-01	4681
1997-01-01	4923
1997-04-01	5374
1997-07-01	5143
1997-10-01	4360
1998-01-01	5071
1998-04-01	4322
1998-07-01	5371
1998-10-01	4702
1999-01-01	5018
1999-04-01	4733
1999-07-01	6358
1999-10-01	4401
2000-01-01	6186
2000-04-01	7468
2000-07-01	8445
2000-10-01	8042
2001-01-01	8192
2001-04-01	7156
2001-07-01	6702
2001-10-01	7105
2002-01-01	7368
2002-04-01	10450
2002-07-01	9193
2002-10-01	8498
2003-01-01	8876
2003-04-01	7794
2003-07-01	8358
2003-10-01	10263
2004-01-01	10222
2004-04-01	10341
2004-07-01	10075
2004-10-01	12821
2005-01-01	11204
2005-04-01	12264
2005-07-01	11002
2005-10-01	11834
2006-01-01	15428
2006-04-01	18619
2006-07-01	20109
2006-10-01	19936
2007-01-01	22046
2007-04-01	21474
2007-07-01	23403
2007-10-01	29470
2008-01-01	37844
2008-04-01	34271
2008-07-01	32351
2008-10-01	35102
2009-01-01	35060
2009-04-01	34090
2009-07-01	37581
2009-10-01	32813
2010-01-01	31077
2010-04-01	33972
2010-07-01	32340
2010-10-01	33221
2011-01-01	38948
2011-04-01	35363
2011-07-01	34890
2011-10-01	33811
2012-01-01	42367
2012-04-01	44987
2012-07-01	46433
2012-10-01	42362
2013-01-01	35341
2013-04-01	34986
2013-07-01	35204
2013-10-01	41816
2014-01-01	40642
2014-04-01	42161
2014-07-01	43296
2014-10-01	37893
2015-01-01	40723
2015-04-01	34225
2015-07-01	33293
2015-10-01	36620
2016-01-01	32450
2016-04-01	38787
2016-07-01	42223
2016-10-01	34426
2017-01-01	38915
2017-04-01	37141
2017-07-01	30824
2017-10-01	29927
2018-01-01	30532
2018-04-01	27836