Quarter	Millions of US Dollars
1997-01-01	16
1997-04-01	21
1997-07-01	21
1997-10-01	21
1998-01-01	21
1998-04-01	22
1998-07-01	22
1998-10-01	22
1999-01-01	22
1999-04-01	21
1999-07-01	21
1999-10-01	21
2000-01-01	21
2000-04-01	16
2000-07-01	16
2000-10-01	16
2001-01-01	16
2001-04-01	16
2001-07-01	16
2001-10-01	16
2002-01-01	16
2002-04-01	16
2002-07-01	16
2002-10-01	16
2003-01-01	16
2003-04-01	16
2003-07-01	16
2003-10-01	16
2004-01-01	16
2004-04-01	16
2004-07-01	16
2004-10-01	16
2016-10-01	550
2017-01-01	550
2017-04-01	550
2017-07-01	550
2017-10-01	550
2018-01-01	550
2018-04-01	550