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	170
1978-07-01	153
1978-10-01	125
1979-01-01	165
1979-04-01	317
1979-07-01	413
1979-10-01	543
1980-01-01	503
1980-04-01	419
1980-07-01	335
1980-10-01	202
1981-01-01	215
1981-04-01	218
1981-07-01	432
1981-10-01	418
1982-01-01	390
1982-04-01	418
1982-07-01	319
1982-10-01	532
1983-01-01	631
1983-04-01	632
1983-07-01	589
1983-10-01	480
1984-01-01	438
1984-04-01	539
1984-07-01	641
1984-10-01	1519
1985-01-01	1615
1985-04-01	1456
1985-07-01	1464
1985-10-01	602
1986-01-01	628
1986-04-01	766
1986-07-01	938
1986-10-01	1235
1987-01-01	1353
1987-04-01	1428
1987-07-01	1282
1987-10-01	1153
1988-01-01	1091
1988-04-01	1147
1988-07-01	1076
1988-10-01	913
1989-01-01	748
1989-04-01	1054
1989-07-01	1296
1989-10-01	1598
1990-01-01	1659
1990-04-01	1125
1990-07-01	999
1990-10-01	795
1991-01-01	584
1991-04-01	504
1991-07-01	571
1991-10-01	766
1992-01-01	695
1992-04-01	1355
1992-07-01	1331
1992-10-01	970
1993-01-01	998
1993-04-01	626
1993-07-01	732
1993-10-01	898
1994-01-01	877
1994-04-01	750
1994-07-01	833
1994-10-01	851
1995-01-01	919
1995-04-01	598
1995-07-01	547
1995-10-01	776
1996-01-01	1095
1996-04-01	1383
1996-07-01	1015
1996-10-01	973
1997-01-01	766
1997-04-01	553
1997-07-01	583
1997-10-01	427
1998-01-01	433
1998-04-01	395
1998-07-01	331
1998-10-01	1271
1999-01-01	1442
1999-04-01	1984
1999-07-01	2113
1999-10-01	1120
2000-01-01	855
2000-04-01	787
2000-07-01	910
2000-10-01	857
2001-01-01	1345
2001-04-01	976
2001-07-01	1229
2001-10-01	1896
2002-01-01	1431
2002-04-01	1472
2002-07-01	956
2002-10-01	1519
2003-01-01	1857
2003-04-01	2437
2003-07-01	2773
2003-10-01	1712
2004-01-01	2153
2004-04-01	2254
2004-07-01	2499
2004-10-01	2646
2005-01-01	2310
2005-04-01	2801
2005-07-01	3621
2005-10-01	5847
2006-01-01	6876
2006-04-01	5221
2006-07-01	8749
2006-10-01	8867
2007-01-01	14152
2007-04-01	15809
2007-07-01	13692
2007-10-01	12330
2008-01-01	12501
2008-04-01	13233
2008-07-01	12918
2008-10-01	15509
2009-01-01	15360
2009-04-01	16389
2009-07-01	16542
2009-10-01	13572
2010-01-01	11503
2010-04-01	15206
2010-07-01	16467
2010-10-01	13345
2011-01-01	15825
2011-04-01	12192
2011-07-01	15713
2011-10-01	19419
2012-01-01	21038
2012-04-01	23740
2012-07-01	21642
2012-10-01	24068
2013-01-01	17953
2013-04-01	21843
2013-07-01	25205
2013-10-01	26239
2014-01-01	30388
2014-04-01	23036
2014-07-01	22850
2014-10-01	23769
2015-01-01	20497
2015-04-01	27743
2015-07-01	27767
2015-10-01	30067
2016-01-01	31701
2016-04-01	27626
2016-07-01	28249
2016-10-01	29631
2017-01-01	33866
2017-04-01	32417
2017-07-01	32596
2017-10-01	28505
2018-01-01	24550
2018-04-01	35275