Year	Number of Years
1960-01-01	63.820
1961-01-01	64.508
1962-01-01	65.181
1963-01-01	65.827
1964-01-01	66.438
1965-01-01	67.022
1966-01-01	67.593
1967-01-01	68.169
1968-01-01	68.756
1969-01-01	69.348
1970-01-01	69.929
1971-01-01	70.476
1972-01-01	70.968
1973-01-01	71.392
1974-01-01	71.748
1975-01-01	72.041
1976-01-01	72.286
1977-01-01	72.504
1978-01-01	72.714
1979-01-01	72.922
1980-01-01	73.130
1981-01-01	73.334
1982-01-01	73.524
1983-01-01	73.693
1984-01-01	73.843
1985-01-01	73.981
1986-01-01	74.116
1987-01-01	74.255
1988-01-01	74.394
1989-01-01	74.526
1990-01-01	74.627
1991-01-01	74.669
1992-01-01	74.634
1993-01-01	74.520
1994-01-01	74.334
1995-01-01	74.100
1996-01-01	73.846
1997-01-01	73.608
1998-01-01	73.417
1999-01-01	73.288
2000-01-01	73.228
2001-01-01	73.230
2002-01-01	73.277
2003-01-01	73.355
2004-01-01	73.465
2005-01-01	73.620
2006-01-01	73.834
2007-01-01	74.116
2008-01-01	74.462
2009-01-01	74.858
2010-01-01	75.280
2011-01-01	75.700
2012-01-01	76.089
2013-01-01	76.430
2014-01-01	76.712
2015-01-01	76.938
2016-01-01	77.116