Year	Number of Years
1960-01-01	59.660
1961-01-01	60.026
1962-01-01	60.386
1963-01-01	60.749
1964-01-01	61.117
1965-01-01	61.491
1966-01-01	61.867
1967-01-01	62.239
1968-01-01	62.599
1969-01-01	62.943
1970-01-01	63.268
1971-01-01	63.568
1972-01-01	63.844
1973-01-01	64.100
1974-01-01	64.339
1975-01-01	64.570
1976-01-01	64.806
1977-01-01	65.054
1978-01-01	65.315
1979-01-01	65.587
1980-01-01	65.863
1981-01-01	66.128
1982-01-01	66.371
1983-01-01	66.582
1984-01-01	66.758
1985-01-01	66.902
1986-01-01	67.019
1987-01-01	67.120
1988-01-01	67.214
1989-01-01	67.305
1990-01-01	67.393
1991-01-01	67.478
1992-01-01	67.554
1993-01-01	67.620
1994-01-01	67.677
1995-01-01	67.722
1996-01-01	67.751
1997-01-01	67.768
1998-01-01	67.781
1999-01-01	67.798
2000-01-01	67.838
2001-01-01	67.918
2002-01-01	68.051
2003-01-01	68.239
2004-01-01	68.480
2005-01-01	68.768
2006-01-01	69.089
2007-01-01	69.422
2008-01-01	69.749
2009-01-01	70.057
2010-01-01	70.335
2011-01-01	70.578
2012-01-01	70.790
2013-01-01	70.976
2014-01-01	71.138
2015-01-01	71.279
2016-01-01	71.405