Year	Hours
1975-01-01	1899
1976-01-01	1896
1977-01-01	1888
1978-01-01	1893
1979-01-01	1869
1980-01-01	1849
1981-01-01	1855
1982-01-01	1840
1983-01-01	1823
1984-01-01	1814
1985-01-01	1813
1986-01-01	1793
1987-01-01	1798
1988-01-01	1806
1989-01-01	1802
1990-01-01	1769
1991-01-01	1747
1992-01-01	1753
1993-01-01	1755
1994-01-01	1775
1995-01-01	1776
1996-01-01	1775
1997-01-01	1771
1998-01-01	1761
1999-01-01	1764
2000-01-01	1751
2001-01-01	1733
2002-01-01	1726
2003-01-01	1719
2004-01-01	1723
2005-01-01	1716
2006-01-01	1709
2007-01-01	1706
2008-01-01	1688
2009-01-01	1673
2010-01-01	1677
2011-01-01	1680