Quarter	Millions of US Dollars
1987-01-01	0
1987-04-01	0
1987-07-01	0
1987-10-01	0
1988-01-01	0
1988-04-01	0
1988-07-01	0
1988-10-01	0
1989-01-01	0
1989-04-01	0
1989-07-01	0
1989-10-01	0
1990-01-01	0
1990-04-01	0
1990-07-01	0
1990-10-01	0
1991-01-01	0
1991-04-01	0
1991-07-01	0
1991-10-01	0
1992-01-01	0
1992-04-01	0
1992-07-01	0
1992-10-01	0
1993-01-01	0
1993-04-01	0
1993-07-01	338
1993-10-01	436
1994-01-01	554
1994-04-01	440
1994-07-01	859
1994-10-01	841
1995-01-01	345
1995-04-01	327
1995-07-01	379
1995-10-01	511
1996-01-01	430
1996-04-01	630
1996-07-01	306
1996-10-01	831
1997-01-01	933
1997-04-01	936
1997-07-01	959
1997-10-01	1240
1998-01-01	1257
1998-04-01	2193
1998-07-01	2716
1998-10-01	2622
1999-01-01	3087
1999-04-01	2310
1999-07-01	3200
1999-10-01	3084
2000-01-01	2661
2000-04-01	2572
2000-07-01	2261
2000-10-01	1611
2001-01-01	1782
2001-04-01	2247
2001-07-01	1789
2001-10-01	2124
2002-01-01	3448
2002-04-01	3431
2002-07-01	3671
2002-10-01	4324
2003-01-01	3910
2003-04-01	4122
2003-07-01	3777
2003-10-01	3689
2004-01-01	4084
2004-04-01	4166
2004-07-01	4558
2004-10-01	6304
2005-01-01	5462
2005-04-01	5718
2005-07-01	6064
2005-10-01	4984
2006-01-01	6034
2006-04-01	6794
2006-07-01	6551
2006-10-01	8296
2007-01-01	13231
2007-04-01	15020
2007-07-01	14206
2007-10-01	14366
2008-01-01	9754
2008-04-01	12612
2008-07-01	17027
2008-10-01	14208
2009-01-01	8671
2009-04-01	10106
2009-07-01	13243
2009-10-01	16494
2010-01-01	16601
2010-04-01	15208
2010-07-01	15090
2010-10-01	13694
2011-01-01	11269
2011-04-01	9834
2011-07-01	9381
2011-10-01	9478
2012-01-01	8604
2012-04-01	9585
2012-07-01	9977
2012-10-01	10856
2013-01-01	11595
2013-04-01	10871
2013-07-01	10205
2013-10-01	7729
2014-01-01	5972
2014-04-01	6329
2014-07-01	5724
2014-10-01	6938
2015-01-01	4745
2015-04-01	2502
2015-07-01	2474
2015-10-01	1930
2016-01-01	5460
2016-04-01	5783
2016-07-01	4038
2016-10-01	3416
2017-01-01	5071
2017-04-01	4982
2017-07-01	4531
2017-10-01	4393
2018-01-01	1348
2018-04-01	850