Year	Hours
1987-01-01	30620000
1988-01-01	30740000
1989-01-01	31010000
1990-01-01	30130000
1991-01-01	28070000
1992-01-01	26080000
1993-01-01	24340000
1994-01-01	24680000
1995-01-01	26100000
1996-01-01	26240000
1997-01-01	25880000
1998-01-01	25620000
1999-01-01	25730000
2000-01-01	25500000
2001-01-01	24650000
2002-01-01	23340000
2003-01-01	22450000
2004-01-01	22220000
2005-01-01	21700000
2006-01-01	21720000
2007-01-01	21810000