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	295
1982-07-01	297
1982-10-01	459
1983-01-01	561
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	943
1985-07-01	1153
1985-10-01	1139
1986-01-01	1076
1986-04-01	1179
1986-07-01	1423
1986-10-01	1019
1987-01-01	1259
1987-04-01	1089
1987-07-01	1201
1987-10-01	1262
1988-01-01	1185
1988-04-01	1537
1988-07-01	1094
1988-10-01	1211
1989-01-01	1212
1989-04-01	918
1989-07-01	1118
1989-10-01	1544
1990-01-01	1993
1990-04-01	2328
1990-07-01	2918
1990-10-01	3998
1991-01-01	4554
1991-04-01	4503
1991-07-01	4576
1991-10-01	4681
1992-01-01	4853
1992-04-01	6152
1992-07-01	7160
1992-10-01	6782
1993-01-01	5831
1993-04-01	5791
1993-07-01	7377
1993-10-01	6262
1994-01-01	6264
1994-04-01	5538
1994-07-01	6117
1994-10-01	6583
1995-01-01	7802
1995-04-01	9060
1995-07-01	10197
1995-10-01	8849
1996-01-01	7986
1996-04-01	7513
1996-07-01	7272
1996-10-01	11461
1997-01-01	11897
1997-04-01	11572
1997-07-01	9977
1997-10-01	8608
1998-01-01	7670
1998-04-01	7487
1998-07-01	7778
1998-10-01	5789
1999-01-01	6685
1999-04-01	6978
1999-07-01	9416
1999-10-01	10019
2000-01-01	7675
2000-04-01	7239
2000-07-01	5856
2000-10-01	5953
2001-01-01	5246
2001-04-01	6425
2001-07-01	7323
2001-10-01	6770
2002-01-01	6594
2002-04-01	7093
2002-07-01	6989
2002-10-01	9517
2003-01-01	8848
2003-04-01	6830
2003-07-01	8867
2003-10-01	7830
2004-01-01	10937
2004-04-01	12064
2004-07-01	8526
2004-10-01	12355
2005-01-01	11992
2005-04-01	9387
2005-07-01	17902
2005-10-01	19461
2006-01-01	22479
2006-04-01	24840
2006-07-01	21695
2006-10-01	21263
2007-01-01	22303
2007-04-01	22637
2007-07-01	22820
2007-10-01	20708
2008-01-01	20213
2008-04-01	29837
2008-07-01	21143
2008-10-01	23426
2009-01-01	24858
2009-04-01	21017
2009-07-01	25725
2009-10-01	26009
2010-01-01	21905
2010-04-01	24945
2010-07-01	26313
2010-10-01	26589
2011-01-01	25930
2011-04-01	25299
2011-07-01	26291
2011-10-01	22411
2012-01-01	24034
2012-04-01	21500
2012-07-01	22595
2012-10-01	21042
2013-01-01	23639
2013-04-01	29130
2013-07-01	28592
2013-10-01	29128
2014-01-01	31864
2014-04-01	26998
2014-07-01	25784
2014-10-01	34178
2015-01-01	33355
2015-04-01	37226
2015-07-01	37006
2015-10-01	29530
2016-01-01	27113
2016-04-01	26411
2016-07-01	30612
2016-10-01	29752
2017-01-01	27654
2017-04-01	31300
2017-07-01	35004
2017-10-01	38593
2018-01-01	44261
2018-04-01	50882