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	247
1979-01-01	537
1979-04-01	738
1979-07-01	979
1979-10-01	1119
1980-01-01	1043
1980-04-01	1455
1980-07-01	1332
1980-10-01	1184
1981-01-01	1335
1981-04-01	1078
1981-07-01	1175
1981-10-01	1238
1982-01-01	1249
1982-04-01	1260
1982-07-01	1269
1982-10-01	1528
1983-01-01	1678
1983-04-01	2498
1983-07-01	2678
1983-10-01	2633
1984-01-01	2708
1984-04-01	1972
1984-07-01	1995
1984-10-01	2407
1985-01-01	2444
1985-04-01	2472
1985-07-01	3102
1985-10-01	3004
1986-01-01	3715
1986-04-01	4293
1986-07-01	4795
1986-10-01	5840
1987-01-01	7178
1987-04-01	8138
1987-07-01	8463
1987-10-01	10460
1988-01-01	10275
1988-04-01	9455
1988-07-01	10973
1988-10-01	11776
1989-01-01	11523
1989-04-01	11421
1989-07-01	11721
1989-10-01	13495
1990-01-01	15107
1990-04-01	18438
1990-07-01	21687
1990-10-01	23757
1991-01-01	26026
1991-04-01	30849
1991-07-01	45291
1991-10-01	51134
1992-01-01	66718
1992-04-01	86017
1992-07-01	95358
1992-10-01	97816
1993-01-01	85979
1993-04-01	67103
1993-07-01	57377
1993-10-01	51568
1994-01-01	48425
1994-04-01	47951
1994-07-01	50855
1994-10-01	46213
1995-01-01	48176
1995-04-01	46373
1995-07-01	38294
1995-10-01	43487
1996-01-01	44804
1996-04-01	48602
1996-07-01	52454
1996-10-01	51259
1997-01-01	54596
1997-04-01	55109
1997-07-01	48053
1997-10-01	37052
1998-01-01	27367
1998-04-01	20939
1998-07-01	19370
1998-10-01	28283
1999-01-01	31576
1999-04-01	32950
1999-07-01	35144
1999-10-01	30158
2000-01-01	23761
2000-04-01	21305
2000-07-01	20845
2000-10-01	19359
2001-01-01	15930
2001-04-01	15128
2001-07-01	15810
2001-10-01	16261
2002-01-01	19097
2002-04-01	19201
2002-07-01	19079
2002-10-01	18019
2003-01-01	17505
2003-04-01	18712
2003-07-01	18602
2003-10-01	17883
2004-01-01	16149
2004-04-01	17908
2004-07-01	15205
2004-10-01	16741
2005-01-01	16072
2005-04-01	13824
2005-07-01	14686
2005-10-01	16581
2006-01-01	20284
2006-04-01	21843
2006-07-01	23474
2006-10-01	18895
2007-01-01	16295
2007-04-01	14202
2007-07-01	13399
2007-10-01	16146
2008-01-01	18728
2008-04-01	24099
2008-07-01	24817
2008-10-01	28422
2009-01-01	24688
2009-04-01	27439
2009-07-01	29716
2009-10-01	25577
2010-01-01	26137
2010-04-01	26881
2010-07-01	30411
2010-10-01	36002
2011-01-01	35384
2011-04-01	30052
2011-07-01	29093
2011-10-01	27796
2012-01-01	25727
2012-04-01	23141
2012-07-01	22846
2012-10-01	21318
2013-01-01	23178
2013-04-01	24794
2013-07-01	24089
2013-10-01	21508
2014-01-01	27002
2014-04-01	33290
2014-07-01	39375
2014-10-01	37983
2015-01-01	35889
2015-04-01	34974
2015-07-01	35492
2015-10-01	36884
2016-01-01	41216
2016-04-01	42321
2016-07-01	44705
2016-10-01	44918
2017-01-01	40622
2017-04-01	46603
2017-07-01	49044
2017-10-01	55228
2018-01-01	55601
2018-04-01	56825