Year	Number of Years
1960-01-01	59.981
1961-01-01	60.531
1962-01-01	61.092
1963-01-01	61.663
1964-01-01	62.241
1965-01-01	62.823
1966-01-01	63.402
1967-01-01	63.971
1968-01-01	64.525
1969-01-01	65.058
1970-01-01	65.566
1971-01-01	66.047
1972-01-01	66.504
1973-01-01	66.939
1974-01-01	67.354
1975-01-01	67.751
1976-01-01	68.135
1977-01-01	68.509
1978-01-01	68.874
1979-01-01	69.229
1980-01-01	69.577
1981-01-01	69.921
1982-01-01	70.257
1983-01-01	70.575
1984-01-01	70.865
1985-01-01	71.110
1986-01-01	71.294
1987-01-01	71.405
1988-01-01	71.437
1989-01-01	71.386
1990-01-01	71.246
1991-01-01	71.011
1992-01-01	70.696
1993-01-01	70.325
1994-01-01	69.922
1995-01-01	69.517
1996-01-01	69.143
1997-01-01	68.820
1998-01-01	68.568
1999-01-01	68.400
2000-01-01	68.329
2001-01-01	68.356
2002-01-01	68.460
2003-01-01	68.619
2004-01-01	68.815
2005-01-01	69.023
2006-01-01	69.218
2007-01-01	69.385
2008-01-01	69.517
2009-01-01	69.611
2010-01-01	69.676
2011-01-01	69.731
2012-01-01	69.798
2013-01-01	69.895
2014-01-01	70.027
2015-01-01	70.192
2016-01-01	70.384