Year	Number of Years
1960-01-01	46.274
1961-01-01	46.953
1962-01-01	47.625
1963-01-01	48.285
1964-01-01	48.926
1965-01-01	49.548
1966-01-01	50.151
1967-01-01	50.742
1968-01-01	51.330
1969-01-01	51.921
1970-01-01	52.523
1971-01-01	53.140
1972-01-01	53.779
1973-01-01	54.440
1974-01-01	55.125
1975-01-01	55.834
1976-01-01	56.567
1977-01-01	57.318
1978-01-01	58.080
1979-01-01	58.851
1980-01-01	59.632
1981-01-01	60.428
1982-01-01	61.236
1983-01-01	62.051
1984-01-01	62.859
1985-01-01	63.643
1986-01-01	64.382
1987-01-01	65.063
1988-01-01	65.679
1989-01-01	66.230
1990-01-01	66.725
1991-01-01	67.180
1992-01-01	67.616
1993-01-01	68.047
1994-01-01	68.476
1995-01-01	68.898
1996-01-01	69.301
1997-01-01	69.672
1998-01-01	70.001
1999-01-01	70.288
2000-01-01	70.537
2001-01-01	70.756
2002-01-01	70.957
2003-01-01	71.150
2004-01-01	71.341
2005-01-01	71.532
2006-01-01	71.724
2007-01-01	71.911
2008-01-01	72.093
2009-01-01	72.270
2010-01-01	72.446
2011-01-01	72.624
2012-01-01	72.805
2013-01-01	72.990
2014-01-01	73.181
2015-01-01	73.376
2016-01-01	73.575