Year	Hours
1971-01-01	1835
1972-01-01	1856
1973-01-01	1865
1974-01-01	1850
1975-01-01	1819
1976-01-01	1812
1977-01-01	1822
1978-01-01	1823
1979-01-01	1820
1980-01-01	1790
1981-01-01	1754
1982-01-01	1750
1983-01-01	1744
1984-01-01	1751
1985-01-01	1753
1986-01-01	1748
1987-01-01	1752
1988-01-01	1759
1989-01-01	1763
1990-01-01	1751
1991-01-01	1725
1992-01-01	1719
1993-01-01	1715
1994-01-01	1725
1995-01-01	1728
1996-01-01	1727
1997-01-01	1725
1998-01-01	1722
1999-01-01	1713
2000-01-01	1698
2001-01-01	1700
2002-01-01	1683
2003-01-01	1673
2004-01-01	1670
2005-01-01	1673
2006-01-01	1668
2007-01-01	1670
2008-01-01	1665
2009-01-01	1643
2010-01-01	1647
2011-01-01	1637