Year	Number of Years
1960-01-01	42.714
1961-01-01	43.384
1962-01-01	44.136
1963-01-01	44.993
1964-01-01	45.950
1965-01-01	46.967
1966-01-01	47.982
1967-01-01	48.927
1968-01-01	49.751
1969-01-01	50.437
1970-01-01	50.989
1971-01-01	51.433
1972-01-01	51.818
1973-01-01	52.189
1974-01-01	52.564
1975-01-01	52.954
1976-01-01	53.361
1977-01-01	53.772
1978-01-01	54.179
1979-01-01	54.581
1980-01-01	54.978
1981-01-01	55.371
1982-01-01	55.761
1983-01-01	56.145
1984-01-01	56.526
1985-01-01	56.904
1986-01-01	57.278
1987-01-01	57.650
1988-01-01	58.018
1989-01-01	58.383
1990-01-01	58.743
1991-01-01	59.099
1992-01-01	59.448
1993-01-01	59.791
1994-01-01	60.128
1995-01-01	60.463
1996-01-01	60.796
1997-01-01	61.131
1998-01-01	61.467
1999-01-01	61.802
2000-01-01	62.133
2001-01-01	62.452
2002-01-01	62.757
2003-01-01	63.046
2004-01-01	63.323
2005-01-01	63.597
2006-01-01	63.880
2007-01-01	64.181
2008-01-01	64.501
2009-01-01	64.838
2010-01-01	65.178
2011-01-01	65.506
2012-01-01	65.805
2013-01-01	66.066
2014-01-01	66.285
2015-01-01	66.464
2016-01-01	66.612