Year	Number of Years
1960-01-01	47.030
1961-01-01	47.677
1962-01-01	48.329
1963-01-01	48.984
1964-01-01	49.642
1965-01-01	50.306
1966-01-01	50.978
1967-01-01	51.657
1968-01-01	52.339
1969-01-01	53.019
1970-01-01	53.685
1971-01-01	54.328
1972-01-01	54.941
1973-01-01	55.517
1974-01-01	56.053
1975-01-01	56.545
1976-01-01	56.991
1977-01-01	57.398
1978-01-01	57.779
1979-01-01	58.146
1980-01-01	58.509
1981-01-01	58.880
1982-01-01	59.271
1983-01-01	59.691
1984-01-01	60.151
1985-01-01	60.670
1986-01-01	61.261
1987-01-01	61.920
1988-01-01	62.637
1989-01-01	63.396
1990-01-01	64.169
1991-01-01	64.927
1992-01-01	65.642
1993-01-01	66.297
1994-01-01	66.886
1995-01-01	67.411
1996-01-01	67.891
1997-01-01	68.349
1998-01-01	68.808
1999-01-01	69.272
2000-01-01	69.742
2001-01-01	70.214
2002-01-01	70.675
2003-01-01	71.117
2004-01-01	71.537
2005-01-01	71.935
2006-01-01	72.313
2007-01-01	72.677
2008-01-01	73.028
2009-01-01	73.369
2010-01-01	73.699
2011-01-01	74.016
2012-01-01	74.319
2013-01-01	74.608
2014-01-01	74.884
2015-01-01	75.149
2016-01-01	75.404