Year	Hours
1970-01-01	1875
1971-01-01	1865
1972-01-01	1839
1973-01-01	1812
1974-01-01	1784
1975-01-01	1775
1976-01-01	1777
1977-01-01	1752
1978-01-01	1735
1979-01-01	1719
1980-01-01	1699
1981-01-01	1676
1982-01-01	1661
1983-01-01	1667
1984-01-01	1691
1985-01-01	1698
1986-01-01	1677
1987-01-01	1662
1988-01-01	1650
1989-01-01	1642
1990-01-01	1655
1991-01-01	1619
1992-01-01	1596
1993-01-01	1552
1994-01-01	1552
1995-01-01	1580
1996-01-01	1554
1997-01-01	1567
1998-01-01	1578
1999-01-01	1581
2000-01-01	1545
2001-01-01	1577
2002-01-01	1580
2003-01-01	1575
2004-01-01	1549
2005-01-01	1565
2006-01-01	1566
2007-01-01	1560
2008-01-01	1568
2009-01-01	1550
2010-01-01	1551
2011-01-01	1551