Year	Number of Years
1960-01-01	62.625
1961-01-01	63.217
1962-01-01	63.723
1963-01-01	64.125
1964-01-01	64.422
1965-01-01	64.621
1966-01-01	64.742
1967-01-01	64.822
1968-01-01	64.892
1969-01-01	64.973
1970-01-01	65.081
1971-01-01	65.228
1972-01-01	65.407
1973-01-01	65.610
1974-01-01	65.833
1975-01-01	66.067
1976-01-01	66.300
1977-01-01	66.519
1978-01-01	66.714
1979-01-01	66.882
1980-01-01	67.022
1981-01-01	67.138
1982-01-01	67.239
1983-01-01	67.335
1984-01-01	67.428
1985-01-01	67.523
1986-01-01	67.620
1987-01-01	67.719
1988-01-01	67.817
1989-01-01	67.914
1990-01-01	68.007
1991-01-01	68.094
1992-01-01	68.171
1993-01-01	68.238
1994-01-01	68.296
1995-01-01	68.344
1996-01-01	68.384
1997-01-01	68.419
1998-01-01	68.452
1999-01-01	68.489
2000-01-01	68.532
2001-01-01	68.584
2002-01-01	68.648
2003-01-01	68.724
2004-01-01	68.816
2005-01-01	68.927
2006-01-01	69.060
2007-01-01	69.214
2008-01-01	69.384
2009-01-01	69.567
2010-01-01	69.756
2011-01-01	69.942
2012-01-01	70.118
2013-01-01	70.280
2014-01-01	70.426
2015-01-01	70.556
2016-01-01	70.673