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	0
1977-10-01	0
1978-01-01	20
1978-04-01	20
1978-07-01	34
1978-10-01	54
1979-01-01	117
1979-04-01	165
1979-07-01	231
1979-10-01	252
1980-01-01	171
1980-04-01	135
1980-07-01	81
1980-10-01	100
1981-01-01	147
1981-04-01	145
1981-07-01	144
1981-10-01	141
1982-01-01	145
1982-04-01	265
1982-07-01	267
1982-10-01	429
1983-01-01	531
1983-04-01	416
1983-07-01	455
1983-10-01	338
1984-01-01	211
1984-04-01	292
1984-07-01	266
1984-10-01	698
1985-01-01	843
1985-04-01	893
1985-07-01	1103
1985-10-01	1089
1986-01-01	1026
1986-04-01	1179
1986-07-01	1423
1986-10-01	1013
1987-01-01	1244
1987-04-01	1074
1987-07-01	1187
1987-10-01	1246
1988-01-01	1085
1988-04-01	1412
1988-07-01	966
1988-10-01	1154
1989-01-01	1245
1989-04-01	978
1989-07-01	1175
1989-10-01	1237
1990-01-01	1627
1990-04-01	1797
1990-07-01	2179
1990-10-01	2913
1991-01-01	3162
1991-04-01	3133
1991-07-01	3301
1991-10-01	3636
1992-01-01	3593
1992-04-01	4809
1992-07-01	5636
1992-10-01	5442
1993-01-01	4939
1993-04-01	4634
1993-07-01	5986
1993-10-01	5052
1994-01-01	5245
1994-04-01	4687
1994-07-01	5114
1994-10-01	5710
1995-01-01	6204
1995-04-01	7213
1995-07-01	7927
1995-10-01	6458
1996-01-01	6921
1996-04-01	6716
1996-07-01	6123
1996-10-01	10309
1997-01-01	11375
1997-04-01	11333
1997-07-01	9684
1997-10-01	8252
1998-01-01	7359
1998-04-01	7376
1998-07-01	7644
1998-10-01	5697
1999-01-01	6477
1999-04-01	6462
1999-07-01	7940
1999-10-01	9360
2000-01-01	7790
2000-04-01	7137
2000-07-01	6232
2000-10-01	5092
2001-01-01	4356
2001-04-01	5242
2001-07-01	5593
2001-10-01	4762
2002-01-01	4479
2002-04-01	5463
2002-07-01	5502
2002-10-01	8270
2003-01-01	8039
2003-04-01	6909
2003-07-01	8952
2003-10-01	6197
2004-01-01	7835
2004-04-01	8270
2004-07-01	5657
2004-10-01	6491
2005-01-01	8711
2005-04-01	6995
2005-07-01	15099
2005-10-01	16262
2006-01-01	19915
2006-04-01	21689
2006-07-01	19375
2006-10-01	19790
2007-01-01	20352
2007-04-01	19358
2007-07-01	20619
2007-10-01	19181
2008-01-01	18950
2008-04-01	26372
2008-07-01	17049
2008-10-01	21180
2009-01-01	21902
2009-04-01	17729
2009-07-01	20307
2009-10-01	21279
2010-01-01	17271
2010-04-01	21108
2010-07-01	21679
2010-10-01	21760
2011-01-01	24256
2011-04-01	22245
2011-07-01	21326
2011-10-01	19285
2012-01-01	21470
2012-04-01	17358
2012-07-01	16955
2012-10-01	18302
2013-01-01	20120
2013-04-01	23772
2013-07-01	24905
2013-10-01	25785
2014-01-01	28279
2014-04-01	24804
2014-07-01	24235
2014-10-01	30123
2015-01-01	30637
2015-04-01	34178
2015-07-01	31902
2015-10-01	25725
2016-01-01	22911
2016-04-01	22757
2016-07-01	26623
2016-10-01	26998
2017-01-01	25209
2017-04-01	28364
2017-07-01	32610
2017-10-01	36274
2018-01-01	39922
2018-04-01	45350