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	10
1977-01-01	10
1977-04-01	10
1977-07-01	10
1977-10-01	0
1978-01-01	16
1978-04-01	59
1978-07-01	71
1978-10-01	232
1979-01-01	445
1979-04-01	548
1979-07-01	785
1979-10-01	865
1980-01-01	832
1980-04-01	1156
1980-07-01	998
1980-10-01	873
1981-01-01	951
1981-04-01	761
1981-07-01	892
1981-10-01	999
1982-01-01	1026
1982-04-01	1109
1982-07-01	1119
1982-10-01	1314
1983-01-01	1450
1983-04-01	2245
1983-07-01	2427
1983-10-01	2326
1984-01-01	2499
1984-04-01	1787
1984-07-01	1680
1984-10-01	2050
1985-01-01	2029
1985-04-01	2097
1985-07-01	2701
1985-10-01	2648
1986-01-01	3130
1986-04-01	3643
1986-07-01	4081
1986-10-01	5194
1987-01-01	6646
1987-04-01	7532
1987-07-01	7977
1987-10-01	9831
1988-01-01	9533
1988-04-01	8533
1988-07-01	10074
1988-10-01	10602
1989-01-01	10386
1989-04-01	10430
1989-07-01	10392
1989-10-01	11761
1990-01-01	12566
1990-04-01	15277
1990-07-01	18012
1990-10-01	19887
1991-01-01	22330
1991-04-01	27447
1991-07-01	39722
1991-10-01	45521
1992-01-01	60039
1992-04-01	78527
1992-07-01	86156
1992-10-01	88484
1993-01-01	76081
1993-04-01	57379
1993-07-01	48000
1993-10-01	43569
1994-01-01	41651
1994-04-01	41560
1994-07-01	42300
1994-10-01	37536
1995-01-01	39568
1995-04-01	38184
1995-07-01	34222
1995-10-01	38736
1996-01-01	40171
1996-04-01	43277
1996-07-01	46118
1996-10-01	44432
1997-01-01	48441
1997-04-01	49630
1997-07-01	44106
1997-10-01	35031
1998-01-01	24859
1998-04-01	18379
1998-07-01	16286
1998-10-01	22509
1999-01-01	25168
1999-04-01	26146
1999-07-01	28124
1999-10-01	24873
2000-01-01	18854
2000-04-01	16568
2000-07-01	13788
2000-10-01	13416
2001-01-01	10616
2001-04-01	8867
2001-07-01	11018
2001-10-01	10035
2002-01-01	12216
2002-04-01	11926
2002-07-01	12199
2002-10-01	10444
2003-01-01	9306
2003-04-01	10057
2003-07-01	9931
2003-10-01	9685
2004-01-01	7228
2004-04-01	7929
2004-07-01	5424
2004-10-01	5386
2005-01-01	6022
2005-04-01	6733
2005-07-01	8653
2005-10-01	10409
2006-01-01	13748
2006-04-01	13643
2006-07-01	12777
2006-10-01	11178
2007-01-01	8700
2007-04-01	7635
2007-07-01	5509
2007-10-01	8692
2008-01-01	9060
2008-04-01	14072
2008-07-01	15158
2008-10-01	15285
2009-01-01	14082
2009-04-01	10712
2009-07-01	10418
2009-10-01	8717
2010-01-01	8252
2010-04-01	11717
2010-07-01	15156
2010-10-01	15553
2011-01-01	14748
2011-04-01	9182
2011-07-01	6228
2011-10-01	4782
2012-01-01	4799
2012-04-01	4959
2012-07-01	5441
2012-10-01	7036
2013-01-01	8170
2013-04-01	7902
2013-07-01	7382
2013-10-01	6289
2014-01-01	7815
2014-04-01	8172
2014-07-01	10028
2014-10-01	9616
2015-01-01	6447
2015-04-01	5873
2015-07-01	4785
2015-10-01	4292
2016-01-01	6034
2016-04-01	6326
2016-07-01	7609
2016-10-01	6719
2017-01-01	5025
2017-04-01	8203
2017-07-01	10256
2017-10-01	11743
2018-01-01	12861
2018-04-01	11436