Quarter	Millions of US Dollars
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	0
1978-04-01	0
1978-07-01	0
1978-10-01	0
1979-01-01	0
1979-04-01	0
1979-07-01	0
1979-10-01	0
1980-01-01	0
1980-04-01	0
1980-07-01	0
1980-10-01	0
1981-01-01	37
1981-04-01	215
1981-07-01	217
1981-10-01	224
1982-01-01	368
1982-04-01	602
1982-07-01	599
1982-10-01	605
1983-01-01	540
1983-04-01	360
1983-07-01	544
1983-10-01	863
1984-01-01	2654
1984-04-01	2599
1984-07-01	2712
1984-10-01	3916
1985-01-01	2929
1985-04-01	3274
1985-07-01	3315
1985-10-01	3251
1986-01-01	2564
1986-04-01	2675
1986-07-01	3194
1986-10-01	2161
1987-01-01	2123
1987-04-01	3954
1987-07-01	3366
1987-10-01	3647
1988-01-01	3665
1988-04-01	1439
1988-07-01	1349
1988-10-01	1310
1989-01-01	1169
1989-04-01	2002
1989-07-01	2249
1989-10-01	1803
1990-01-01	1921
1990-04-01	689
1990-07-01	593
1990-10-01	2020
1991-01-01	2078
1991-04-01	1855
1991-07-01	2310
1991-10-01	1575
1992-01-01	1499
1992-04-01	2426
1992-07-01	1866
1992-10-01	1842
1993-01-01	2755
1993-04-01	2361
1993-07-01	8814
1993-10-01	8312
1994-01-01	7661
1994-04-01	7871
1994-07-01	8895
1994-10-01	14730
1995-01-01	14419
1995-04-01	14037
1995-07-01	13637
1995-10-01	12289
1996-01-01	13382
1996-04-01	14212
1996-07-01	10840
1996-10-01	14919
1997-01-01	12810
1997-04-01	14752
1997-07-01	14863
1997-10-01	12297
1998-01-01	11317
1998-04-01	12262
1998-07-01	11588
1998-10-01	9803
1999-01-01	7899
1999-04-01	6568
1999-07-01	8075
1999-10-01	6643
2000-01-01	5694
2000-04-01	4630
2000-07-01	3884
2000-10-01	4037
2001-01-01	2790
2001-04-01	3185
2001-07-01	2660
2001-10-01	3710
2002-01-01	5436
2002-04-01	6420
2002-07-01	5700
2002-10-01	4826
2003-01-01	4147
2003-04-01	3212
2003-07-01	2788
2003-10-01	2688
2004-01-01	1331
2004-04-01	1420
2004-07-01	1419
2004-10-01	4113
2005-01-01	4258
2005-04-01	3902
2005-07-01	4126
2005-10-01	1841
2006-01-01	2157
2006-04-01	2134
2006-07-01	1962
2006-10-01	2501
2007-01-01	2821
2007-04-01	3231
2007-07-01	3020
2007-10-01	7043
2008-01-01	7768
2008-04-01	8925
2008-07-01	7685
2008-10-01	7551
2009-01-01	3639
2009-04-01	8646
2009-07-01	8990
2009-10-01	8592
2010-01-01	12984
2010-04-01	8380
2010-07-01	12727
2010-10-01	18016
2011-01-01	13091
2011-04-01	9488
2011-07-01	5813
2011-10-01	12502
2012-01-01	6811
2012-04-01	5723
2012-07-01	8355
2012-10-01	17487
2013-01-01	17398
2013-04-01	17509
2013-07-01	18629
2013-10-01	21720
2014-01-01	22514
2014-04-01	22477
2014-07-01	23439
2014-10-01	29967
2015-01-01	20089
2015-04-01	9447
2015-07-01	13311
2015-10-01	19948
2016-01-01	13618
2016-04-01	15441
2016-07-01	16286
2016-10-01	19017
2017-01-01	24896
2017-04-01	20960
2017-07-01	17267
2017-10-01	14767
2018-01-01	6336
2018-04-01	6718