Year	Number of Years
1960-01-01	46.702
1961-01-01	47.219
1962-01-01	47.750
1963-01-01	48.295
1964-01-01	48.856
1965-01-01	49.434
1966-01-01	50.032
1967-01-01	50.646
1968-01-01	51.267
1969-01-01	51.889
1970-01-01	52.501
1971-01-01	53.091
1972-01-01	53.652
1973-01-01	54.181
1974-01-01	54.676
1975-01-01	55.140
1976-01-01	55.577
1977-01-01	56.000
1978-01-01	56.418
1979-01-01	56.840
1980-01-01	57.272
1981-01-01	57.719
1982-01-01	58.183
1983-01-01	58.661
1984-01-01	59.154
1985-01-01	59.661
1986-01-01	60.176
1987-01-01	60.694
1988-01-01	61.214
1989-01-01	61.735
1990-01-01	62.261
1991-01-01	62.799
1992-01-01	63.352
1993-01-01	63.921
1994-01-01	64.502
1995-01-01	65.090
1996-01-01	65.678
1997-01-01	66.257
1998-01-01	66.817
1999-01-01	67.351
2000-01-01	67.849
2001-01-01	68.304
2002-01-01	68.717
2003-01-01	69.092
2004-01-01	69.437
2005-01-01	69.763
2006-01-01	70.085
2007-01-01	70.415
2008-01-01	70.760
2009-01-01	71.122
2010-01-01	71.494
2011-01-01	71.867
2012-01-01	72.227
2013-01-01	72.562
2014-01-01	72.869
2015-01-01	73.150
2016-01-01	73.409