Year	Hours
1970-01-01	1966
1971-01-01	1934
1972-01-01	1911
1973-01-01	1883
1974-01-01	1843
1975-01-01	1806
1976-01-01	1819
1977-01-01	1801
1978-01-01	1782
1979-01-01	1770
1980-01-01	1751
1981-01-01	1729
1982-01-01	1718
1983-01-01	1705
1984-01-01	1694
1985-01-01	1671
1986-01-01	1652
1987-01-01	1629
1988-01-01	1624
1989-01-01	1601
1990-01-01	1578
1991-01-01	1552
1992-01-01	1564
1993-01-01	1547
1994-01-01	1545
1995-01-01	1529
1996-01-01	1511
1997-01-01	1505
1998-01-01	1499
1999-01-01	1491
2000-01-01	1471
2001-01-01	1453
2002-01-01	1441
2003-01-01	1436
2004-01-01	1436
2005-01-01	1431
2006-01-01	1424
2007-01-01	1422
2008-01-01	1422
2009-01-01	1383
2010-01-01	1408
2011-01-01	1411