Year	Number of Years
1960-01-01	63.651
1961-01-01	64.058
1962-01-01	64.468
1963-01-01	64.880
1964-01-01	65.291
1965-01-01	65.694
1966-01-01	66.083
1967-01-01	66.454
1968-01-01	66.805
1969-01-01	67.136
1970-01-01	67.452
1971-01-01	67.766
1972-01-01	68.082
1973-01-01	68.401
1974-01-01	68.718
1975-01-01	69.014
1976-01-01	69.266
1977-01-01	69.461
1978-01-01	69.592
1979-01-01	69.665
1980-01-01	69.700
1981-01-01	69.726
1982-01-01	69.768
1983-01-01	69.844
1984-01-01	69.954
1985-01-01	70.083
1986-01-01	70.204
1987-01-01	70.288
1988-01-01	70.323
1989-01-01	70.311
1990-01-01	70.268
1991-01-01	70.220
1992-01-01	70.196
1993-01-01	70.222
1994-01-01	70.307
1995-01-01	70.462
1996-01-01	70.687
1997-01-01	70.966
1998-01-01	71.274
1999-01-01	71.596
2000-01-01	71.907
2001-01-01	72.182
2002-01-01	72.408
2003-01-01	72.575
2004-01-01	72.682
2005-01-01	72.730
2006-01-01	72.730
2007-01-01	72.704
2008-01-01	72.673
2009-01-01	72.650
2010-01-01	72.649
2011-01-01	72.680
2012-01-01	72.742
2013-01-01	72.832
2014-01-01	72.951
2015-01-01	73.096
2016-01-01	73.261