Year	Number of Years
1960-01-01	65.971
1961-01-01	66.402
1962-01-01	66.837
1963-01-01	67.276
1964-01-01	67.715
1965-01-01	68.152
1966-01-01	68.587
1967-01-01	69.015
1968-01-01	69.425
1969-01-01	69.808
1970-01-01	70.143
1971-01-01	70.411
1972-01-01	70.604
1973-01-01	70.723
1974-01-01	70.774
1975-01-01	70.783
1976-01-01	70.783
1977-01-01	70.798
1978-01-01	70.838
1979-01-01	70.897
1980-01-01	70.938
1981-01-01	70.910
1982-01-01	70.776
1983-01-01	70.519
1984-01-01	70.150
1985-01-01	69.698
1986-01-01	69.205
1987-01-01	68.732
1988-01-01	68.332
1989-01-01	68.038
1990-01-01	67.879
1991-01-01	67.870
1992-01-01	67.990
1993-01-01	68.218
1994-01-01	68.538
1995-01-01	68.938
1996-01-01	69.404
1997-01-01	69.912
1998-01-01	70.434
1999-01-01	70.944
2000-01-01	71.409
2001-01-01	71.800
2002-01-01	72.112
2003-01-01	72.347
2004-01-01	72.512
2005-01-01	72.625
2006-01-01	72.715
2007-01-01	72.815
2008-01-01	72.946
2009-01-01	73.119
2010-01-01	73.331
2011-01-01	73.571
2012-01-01	73.814
2013-01-01	74.044
2014-01-01	74.255
2015-01-01	74.445
2016-01-01	74.618