Year	Hours
1977-01-01	1923
1978-01-01	1900
1979-01-01	1849
1980-01-01	1835
1981-01-01	1807
1982-01-01	1807
1983-01-01	1775
1984-01-01	1738
1985-01-01	1720
1986-01-01	1720
1987-01-01	1670
1988-01-01	1675
1989-01-01	1684
1990-01-01	1684
1991-01-01	1675
1992-01-01	1671
1993-01-01	1662
1994-01-01	1659
1995-01-01	1667
1996-01-01	1666
1997-01-01	1677
1998-01-01	1690
1999-01-01	1706
2000-01-01	1731
2001-01-01	1736
2002-01-01	1734
2003-01-01	1719
2004-01-01	1704
2005-01-01	1686
2006-01-01	1673
2007-01-01	1658
2008-01-01	1663
2009-01-01	1669
2010-01-01	1674
2011-01-01	1692