Year	Number of Years
1960-01-01	48.651
1961-01-01	49.281
1962-01-01	49.897
1963-01-01	50.499
1964-01-01	51.090
1965-01-01	51.672
1966-01-01	52.249
1967-01-01	52.824
1968-01-01	53.397
1969-01-01	53.968
1970-01-01	54.537
1971-01-01	55.100
1972-01-01	55.655
1973-01-01	56.197
1974-01-01	56.726
1975-01-01	57.240
1976-01-01	57.742
1977-01-01	58.230
1978-01-01	58.707
1979-01-01	59.171
1980-01-01	59.618
1981-01-01	60.045
1982-01-01	60.451
1983-01-01	60.836
1984-01-01	61.203
1985-01-01	61.555
1986-01-01	61.899
1987-01-01	62.241
1988-01-01	62.583
1989-01-01	62.929
1990-01-01	63.281
1991-01-01	63.638
1992-01-01	63.998
1993-01-01	64.353
1994-01-01	64.701
1995-01-01	65.032
1996-01-01	65.339
1997-01-01	65.617
1998-01-01	65.866
1999-01-01	66.087
2000-01-01	66.285
2001-01-01	66.467
2002-01-01	66.643
2003-01-01	66.820
2004-01-01	67.002
2005-01-01	67.191
2006-01-01	67.386
2007-01-01	67.581
2008-01-01	67.775
2009-01-01	67.964
2010-01-01	68.150
2011-01-01	68.331
2012-01-01	68.509
2013-01-01	68.684
2014-01-01	68.856
2015-01-01	69.025
2016-01-01	69.191