Quarter	Millions of US Dollars
1985-01-01	20
1985-04-01	20
1985-07-01	23
1985-10-01	25
1986-01-01	28
1986-04-01	31
1986-07-01	60
1986-10-01	58
1987-01-01	64
1987-04-01	63
1987-07-01	64
1987-10-01	77
1988-01-01	75
1988-04-01	107
1988-07-01	106
1988-10-01	114
1989-01-01	108
1989-04-01	99
1989-07-01	103
1989-10-01	100
1990-01-01	59
1990-04-01	61
1990-07-01	67
1990-10-01	69
1991-01-01	66
1991-04-01	67
1991-07-01	38
1991-10-01	40
1992-01-01	38
1992-04-01	40
1992-07-01	42
1992-10-01	40
1993-01-01	43
1993-04-01	47
1993-07-01	47
1993-10-01	45
1994-01-01	49
1994-04-01	64
1994-07-01	64
1994-10-01	94
1995-01-01	101
1995-04-01	102
1995-07-01	94
1995-10-01	92
1996-01-01	90
1996-04-01	89
1996-07-01	88
1996-10-01	86
1997-01-01	84
1997-04-01	74
1997-07-01	71
1997-10-01	68
1998-01-01	68
1998-04-01	30
1998-07-01	30
1998-10-01	30
1999-01-01	30
1999-04-01	30
1999-07-01	30
2000-04-01	100
2000-07-01	100
2000-10-01	100
2001-01-01	100
2001-04-01	100
2001-07-01	100
2001-10-01	250
2002-01-01	250
2002-04-01	250
2002-07-01	250
2002-10-01	250
2003-01-01	250
2003-04-01	250
2003-07-01	250
2003-10-01	250
2004-01-01	250
2004-04-01	250
2004-07-01	250
2004-10-01	250
2005-01-01	250
2005-04-01	250
2005-07-01	250
2005-10-01	375
2006-01-01	375
2006-04-01	375
2006-07-01	375
2006-10-01	440
2007-01-01	440
2007-04-01	440
2007-07-01	440
2007-10-01	440
2008-01-01	440
2008-04-01	440
2008-07-01	440
2008-10-01	440
2009-01-01	440
2009-04-01	440
2009-07-01	440
2009-10-01	440
2010-01-01	440
2010-04-01	340
2010-07-01	540
2010-10-01	540
2011-01-01	540
2011-04-01	540
2011-07-01	540
2011-10-01	540
2012-01-01	540
2012-04-01	540
2012-07-01	540
2012-10-01	540
2013-01-01	540
2013-04-01	540
2013-07-01	540
2013-10-01	540
2014-01-01	540
2014-04-01	540
2014-07-01	540
2014-10-01	540
2015-01-01	540
2015-04-01	540
2015-07-01	540
2015-10-01	540
2016-01-01	540
2016-04-01	540
2016-07-01	540
2016-10-01	540
2017-01-01	540
2017-04-01	540
2017-07-01	540
2017-10-01	540
2018-01-01	540
2018-04-01	540