Year	Hours
1980-01-01	1531
1981-01-01	1522
1982-01-01	1537
1983-01-01	1546
1984-01-01	1548
1985-01-01	1552
1986-01-01	1550
1987-01-01	1561
1988-01-01	1580
1989-01-01	1579
1990-01-01	1575
1991-01-01	1562
1992-01-01	1580
1993-01-01	1597
1994-01-01	1635
1995-01-01	1640
1996-01-01	1653
1997-01-01	1658
1998-01-01	1657
1999-01-01	1665
2000-01-01	1642
2001-01-01	1619
2002-01-01	1595
2003-01-01	1582
2004-01-01	1606
2005-01-01	1605
2006-01-01	1599
2007-01-01	1612
2008-01-01	1617
2009-01-01	1609
2010-01-01	1643
2011-01-01	1643