Year	Number of Years
1960-01-01	42.021
1961-01-01	42.656
1962-01-01	43.351
1963-01-01	44.109
1964-01-01	44.931
1965-01-01	45.820
1966-01-01	46.780
1967-01-01	47.804
1968-01-01	48.881
1969-01-01	50.000
1970-01-01	51.145
1971-01-01	52.300
1972-01-01	53.452
1973-01-01	54.591
1974-01-01	55.705
1975-01-01	56.795
1976-01-01	57.867
1977-01-01	58.929
1978-01-01	59.980
1979-01-01	61.010
1980-01-01	62.000
1981-01-01	62.925
1982-01-01	63.771
1983-01-01	64.532
1984-01-01	65.214
1985-01-01	65.834
1986-01-01	66.417
1987-01-01	66.991
1988-01-01	67.576
1989-01-01	68.176
1990-01-01	68.788
1991-01-01	69.401
1992-01-01	69.990
1993-01-01	70.540
1994-01-01	71.043
1995-01-01	71.496
1996-01-01	71.898
1997-01-01	72.259
1998-01-01	72.586
1999-01-01	72.883
2000-01-01	73.155
2001-01-01	73.402
2002-01-01	73.629
2003-01-01	73.836
2004-01-01	74.026
2005-01-01	74.200
2006-01-01	74.352
2007-01-01	74.483
2008-01-01	74.595
2009-01-01	74.695
2010-01-01	74.793
2011-01-01	74.900
2012-01-01	75.023
2013-01-01	75.167
2014-01-01	75.335
2015-01-01	75.525
2016-01-01	75.731