Year	Number of Years
1960-01-01	51.787
1961-01-01	52.519
1962-01-01	53.237
1963-01-01	53.943
1964-01-01	54.634
1965-01-01	55.312
1966-01-01	55.975
1967-01-01	56.625
1968-01-01	57.259
1969-01-01	57.875
1970-01-01	58.468
1971-01-01	59.033
1972-01-01	59.569
1973-01-01	60.073
1974-01-01	60.549
1975-01-01	60.997
1976-01-01	61.417
1977-01-01	61.817
1978-01-01	62.205
1979-01-01	62.588
1980-01-01	62.977
1981-01-01	63.380
1982-01-01	63.803
1983-01-01	64.247
1984-01-01	64.714
1985-01-01	65.207
1986-01-01	65.728
1987-01-01	66.267
1988-01-01	66.812
1989-01-01	67.352
1990-01-01	67.866
1991-01-01	68.335
1992-01-01	68.749
1993-01-01	69.103
1994-01-01	69.397
1995-01-01	69.637
1996-01-01	69.837
1997-01-01	70.017
1998-01-01	70.193
1999-01-01	70.374
2000-01-01	70.568
2001-01-01	70.775
2002-01-01	70.990
2003-01-01	71.207
2004-01-01	71.425
2005-01-01	71.644
2006-01-01	71.862
2007-01-01	72.078
2008-01-01	72.290
2009-01-01	72.498
2010-01-01	72.702
2011-01-01	72.901
2012-01-01	73.098
2013-01-01	73.292
2014-01-01	73.483
2015-01-01	73.673
2016-01-01	73.861