Year	Number of Years
1960-01-01	28.199
1961-01-01	28.345
1962-01-01	28.535
1963-01-01	28.782
1964-01-01	29.097
1965-01-01	29.489
1966-01-01	29.959
1967-01-01	30.496
1968-01-01	31.086
1969-01-01	31.720
1970-01-01	32.388
1971-01-01	33.078
1972-01-01	33.782
1973-01-01	34.493
1974-01-01	35.205
1975-01-01	35.921
1976-01-01	36.645
1977-01-01	37.385
1978-01-01	38.142
1979-01-01	38.909
1980-01-01	39.677
1981-01-01	40.435
1982-01-01	41.173
1983-01-01	41.879
1984-01-01	42.545
1985-01-01	43.170
1986-01-01	43.759
1987-01-01	44.315
1988-01-01	44.838
1989-01-01	45.323
1990-01-01	45.746
1991-01-01	46.076
1992-01-01	46.305
1993-01-01	46.445
1994-01-01	46.520
1995-01-01	46.573
1996-01-01	46.658
1997-01-01	46.823
1998-01-01	47.103
1999-01-01	47.515
2000-01-01	48.069
2001-01-01	48.758
2002-01-01	49.540
2003-01-01	50.373
2004-01-01	51.224
2005-01-01	52.057
2006-01-01	52.839
2007-01-01	53.553
2008-01-01	54.193
2009-01-01	54.756
2010-01-01	55.249
2011-01-01	55.694
2012-01-01	56.122
2013-01-01	56.556
2014-01-01	57.007
2015-01-01	57.478
2016-01-01	57.966