Year	Number of Years
1960-01-01	48.928
1961-01-01	49.123
1962-01-01	49.400
1963-01-01	49.771
1964-01-01	50.235
1965-01-01	50.772
1966-01-01	51.349
1967-01-01	51.934
1968-01-01	52.511
1969-01-01	53.078
1970-01-01	53.669
1971-01-01	54.331
1972-01-01	55.096
1973-01-01	55.973
1974-01-01	56.940
1975-01-01	57.950
1976-01-01	58.937
1977-01-01	59.837
1978-01-01	60.606
1979-01-01	61.228
1980-01-01	61.708
1981-01-01	62.073
1982-01-01	62.376
1983-01-01	62.664
1984-01-01	62.958
1985-01-01	63.268
1986-01-01	63.592
1987-01-01	63.918
1988-01-01	64.238
1989-01-01	64.556
1990-01-01	64.877
1991-01-01	65.204
1992-01-01	65.543
1993-01-01	65.902
1994-01-01	66.288
1995-01-01	66.720
1996-01-01	67.221
1997-01-01	67.793
1998-01-01	68.421
1999-01-01	69.086
2000-01-01	69.747
2001-01-01	70.358
2002-01-01	70.882
2003-01-01	71.293
2004-01-01	71.584
2005-01-01	71.760
2006-01-01	71.842
2007-01-01	71.869
2008-01-01	71.881
2009-01-01	71.899
2010-01-01	71.941
2011-01-01	72.019
2012-01-01	72.127
2013-01-01	72.259
2014-01-01	72.418
2015-01-01	72.599
2016-01-01	72.798