Year	Number of Years
1960-01-01	55.860
1961-01-01	56.292
1962-01-01	56.716
1963-01-01	57.133
1964-01-01	57.545
1965-01-01	57.950
1966-01-01	58.350
1967-01-01	58.741
1968-01-01	59.123
1969-01-01	59.495
1970-01-01	59.857
1971-01-01	60.207
1972-01-01	60.546
1973-01-01	60.873
1974-01-01	61.191
1975-01-01	61.500
1976-01-01	61.803
1977-01-01	62.102
1978-01-01	62.397
1979-01-01	62.689
1980-01-01	62.978
1981-01-01	63.262
1982-01-01	63.540
1983-01-01	63.811
1984-01-01	64.074
1985-01-01	64.329
1986-01-01	64.577
1987-01-01	64.818
1988-01-01	65.054
1989-01-01	65.284
1990-01-01	65.510
1991-01-01	65.731
1992-01-01	65.948
1993-01-01	66.161
1994-01-01	66.370
1995-01-01	66.575
1996-01-01	66.777
1997-01-01	66.976
1998-01-01	67.172
1999-01-01	67.365
2000-01-01	67.553
2001-01-01	67.734
2002-01-01	67.910
2003-01-01	68.079
2004-01-01	68.243
2005-01-01	68.405
2006-01-01	68.569
2007-01-01	68.737
2008-01-01	68.909
2009-01-01	69.087
2010-01-01	69.267
2011-01-01	69.448
2012-01-01	69.625
2013-01-01	69.796
2014-01-01	69.960
2015-01-01	70.117
2016-01-01	70.269