Year	Number of Years
1960-01-01	34.890
1961-01-01	35.086
1962-01-01	35.266
1963-01-01	35.432
1964-01-01	35.588
1965-01-01	35.740
1966-01-01	35.891
1967-01-01	36.048
1968-01-01	36.222
1969-01-01	36.421
1970-01-01	36.656
1971-01-01	36.933
1972-01-01	37.255
1973-01-01	37.623
1974-01-01	38.039
1975-01-01	38.498
1976-01-01	38.993
1977-01-01	39.517
1978-01-01	40.068
1979-01-01	40.650
1980-01-01	41.279
1981-01-01	41.977
1982-01-01	42.753
1983-01-01	43.607
1984-01-01	44.522
1985-01-01	45.482
1986-01-01	46.463
1987-01-01	47.434
1988-01-01	48.359
1989-01-01	49.208
1990-01-01	49.949
1991-01-01	50.557
1992-01-01	51.032
1993-01-01	51.381
1994-01-01	51.610
1995-01-01	51.717
1996-01-01	51.701
1997-01-01	51.592
1998-01-01	51.434
1999-01-01	51.273
2000-01-01	51.181
2001-01-01	51.229
2002-01-01	51.451
2003-01-01	51.859
2004-01-01	52.444
2005-01-01	53.170
2006-01-01	53.972
2007-01-01	54.775
2008-01-01	55.521
2009-01-01	56.185
2010-01-01	56.765
2011-01-01	57.282
2012-01-01	57.782
2013-01-01	58.301
2014-01-01	58.846
2015-01-01	59.419
2016-01-01	60.015