Year	Number of Years
1960-01-01	60.285
1961-01-01	61.010
1962-01-01	61.697
1963-01-01	62.346
1964-01-01	62.961
1965-01-01	63.542
1966-01-01	64.092
1967-01-01	64.614
1968-01-01	65.108
1969-01-01	65.579
1970-01-01	66.027
1971-01-01	66.453
1972-01-01	66.857
1973-01-01	67.241
1974-01-01	67.607
1975-01-01	67.958
1976-01-01	68.298
1977-01-01	68.628
1978-01-01	68.949
1979-01-01	69.263
1980-01-01	69.573
1981-01-01	69.878
1982-01-01	70.178
1983-01-01	70.470
1984-01-01	70.752
1985-01-01	71.021
1986-01-01	71.273
1987-01-01	71.505
1988-01-01	71.717
1989-01-01	71.908
1990-01-01	72.079
1991-01-01	72.232
1992-01-01	72.369
1993-01-01	72.496
1994-01-01	72.613
1995-01-01	72.722
1996-01-01	72.824
1997-01-01	72.917
1998-01-01	73.004
1999-01-01	73.084
2000-01-01	73.160
2001-01-01	73.232
2002-01-01	73.300
2003-01-01	73.367
2004-01-01	73.434
2005-01-01	73.505
2006-01-01	73.584
2007-01-01	73.670
2008-01-01	73.764
2009-01-01	73.868
2010-01-01	73.979
2011-01-01	74.096
2012-01-01	74.217
2013-01-01	74.338
2014-01-01	74.458
2015-01-01	74.577
2016-01-01	74.694