Year	Number of Years
1960-01-01	67.782
1961-01-01	68.006
1962-01-01	68.197
1963-01-01	68.347
1964-01-01	68.454
1965-01-01	68.521
1966-01-01	68.554
1967-01-01	68.568
1968-01-01	68.576
1969-01-01	68.589
1970-01-01	68.617
1971-01-01	68.664
1972-01-01	68.732
1973-01-01	68.823
1974-01-01	68.939
1975-01-01	69.087
1976-01-01	69.269
1977-01-01	69.482
1978-01-01	69.721
1979-01-01	69.981
1980-01-01	70.255
1981-01-01	70.535
1982-01-01	70.814
1983-01-01	71.085
1984-01-01	71.343
1985-01-01	71.584
1986-01-01	71.805
1987-01-01	72.009
1988-01-01	72.203
1989-01-01	72.388
1990-01-01	72.571
1991-01-01	72.758
1992-01-01	72.954
1993-01-01	73.161
1994-01-01	73.381
1995-01-01	73.613
1996-01-01	73.854
1997-01-01	74.098
1998-01-01	74.341
1999-01-01	74.577
2000-01-01	74.805
2001-01-01	75.022
2002-01-01	75.229
2003-01-01	75.427
2004-01-01	75.614
2005-01-01	75.792
2006-01-01	75.961
2007-01-01	76.124
2008-01-01	76.282
2009-01-01	76.436
2010-01-01	76.588
2011-01-01	76.739
2012-01-01	76.890
2013-01-01	77.040
2014-01-01	77.190
2015-01-01	77.341
2016-01-01	77.493