Year	Number of Years
1960-01-01	46.910
1961-01-01	47.535
1962-01-01	48.145
1963-01-01	48.740
1964-01-01	49.320
1965-01-01	49.879
1966-01-01	50.411
1967-01-01	50.917
1968-01-01	51.400
1969-01-01	51.869
1970-01-01	52.338
1971-01-01	52.830
1972-01-01	53.354
1973-01-01	53.914
1974-01-01	54.503
1975-01-01	55.102
1976-01-01	55.684
1977-01-01	56.224
1978-01-01	56.708
1979-01-01	57.135
1980-01-01	57.521
1981-01-01	57.892
1982-01-01	58.275
1983-01-01	58.685
1984-01-01	59.122
1985-01-01	59.584
1986-01-01	60.063
1987-01-01	60.533
1988-01-01	60.957
1989-01-01	61.307
1990-01-01	61.539
1991-01-01	61.614
1992-01-01	61.518
1993-01-01	61.247
1994-01-01	60.806
1995-01-01	60.192
1996-01-01	59.407
1997-01-01	58.495
1998-01-01	57.517
1999-01-01	56.533
2000-01-01	55.608
2001-01-01	54.798
2002-01-01	54.145
2003-01-01	53.693
2004-01-01	53.480
2005-01-01	53.563
2006-01-01	53.983
2007-01-01	54.712
2008-01-01	55.697
2009-01-01	56.883
2010-01-01	58.189
2011-01-01	59.527
2012-01-01	60.815
2013-01-01	61.982
2014-01-01	62.981
2015-01-01	63.782
2016-01-01	64.388