Year	Number of Years
1960-01-01	53.236
1961-01-01	53.842
1962-01-01	54.409
1963-01-01	54.932
1964-01-01	55.407
1965-01-01	55.840
1966-01-01	56.237
1967-01-01	56.615
1968-01-01	56.992
1969-01-01	57.377
1970-01-01	57.783
1971-01-01	58.216
1972-01-01	58.678
1973-01-01	59.167
1974-01-01	59.682
1975-01-01	60.222
1976-01-01	60.781
1977-01-01	61.353
1978-01-01	61.930
1979-01-01	62.511
1980-01-01	63.095
1981-01-01	63.686
1982-01-01	64.286
1983-01-01	64.896
1984-01-01	65.511
1985-01-01	66.126
1986-01-01	66.735
1987-01-01	67.332
1988-01-01	67.910
1989-01-01	68.464
1990-01-01	68.990
1991-01-01	69.487
1992-01-01	69.956
1993-01-01	70.400
1994-01-01	70.820
1995-01-01	71.217
1996-01-01	71.594
1997-01-01	71.953
1998-01-01	72.297
1999-01-01	72.624
2000-01-01	72.933
2001-01-01	73.220
2002-01-01	73.482
2003-01-01	73.720
2004-01-01	73.937
2005-01-01	74.136
2006-01-01	74.322
2007-01-01	74.501
2008-01-01	74.678
2009-01-01	74.859
2010-01-01	75.046
2011-01-01	75.244
2012-01-01	75.449
2013-01-01	75.661
2014-01-01	75.879
2015-01-01	76.102
2016-01-01	76.327