Quarter	Hours
1987-01-01	32600000
1987-04-01	31240000
1987-07-01	26370000
1987-10-01	32250000
1988-01-01	32320000
1988-04-01	31610000
1988-07-01	26670000
1988-10-01	32370000
1989-01-01	32960000
1989-04-01	31710000
1989-07-01	27090000
1989-10-01	32300000
1990-01-01	32470000
1990-04-01	30810000
1990-07-01	26430000
1990-10-01	30810000
1991-01-01	30890000
1991-04-01	28920000
1991-07-01	23940000
1991-10-01	28540000
1992-01-01	28560000
1992-04-01	26880000
1992-07-01	22150000
1992-10-01	26730000
1993-01-01	25960000
1993-04-01	24730000
1993-07-01	21320000
1993-10-01	25380000
1994-01-01	25030000
1994-04-01	25240000
1994-07-01	21530000
1994-10-01	26950000
1995-01-01	27370000
1995-04-01	25790000
1995-07-01	22980000
1995-10-01	28270000
1996-01-01	28340000
1996-04-01	26530000
1996-07-01	22330000
1996-10-01	27770000
1997-01-01	26320000
1997-04-01	26630000
1997-07-01	22710000
1997-10-01	27860000
1998-01-01	26360000
1998-04-01	26510000
1998-07-01	22970000
1998-10-01	26590000
1999-01-01	26940000
1999-04-01	26590000
1999-07-01	22610000
1999-10-01	26780000
2000-01-01	26870000
2000-04-01	25820000
2000-07-01	22230000
2000-10-01	27090000
2001-01-01	27110000
2001-04-01	24950000
2001-07-01	21040000
2001-10-01	25510000
2002-01-01	24680000
2002-04-01	24070000
2002-07-01	20120000
2002-10-01	24490000
2003-01-01	23650000
2003-04-01	23170000
2003-07-01	19290000
2003-10-01	23690000
2004-01-01	22700000
2004-04-01	23050000
2004-07-01	19330000
2004-10-01	23680000
2005-01-01	22980000
2005-04-01	23360000
2005-07-01	18520000
2005-10-01	22980000
2006-01-01	22960000
2006-04-01	21820000
2006-07-01	19090000
2006-10-01	22990000
2007-01-01	23380000
2007-04-01	22120000
2007-07-01	18850000
2007-10-01	22890000
2008-01-01	22200000
2008-04-01	23170000
2008-07-01	18380000