Year	Number of Years
1960-01-01	54.703
1961-01-01	55.235
1962-01-01	55.747
1963-01-01	56.233
1964-01-01	56.694
1965-01-01	57.136
1966-01-01	57.567
1967-01-01	58.000
1968-01-01	58.444
1969-01-01	58.905
1970-01-01	59.387
1971-01-01	59.888
1972-01-01	60.405
1973-01-01	60.930
1974-01-01	61.460
1975-01-01	61.986
1976-01-01	62.496
1977-01-01	62.987
1978-01-01	63.464
1979-01-01	63.936
1980-01-01	64.433
1981-01-01	64.993
1982-01-01	65.635
1983-01-01	66.353
1984-01-01	67.128
1985-01-01	67.911
1986-01-01	68.642
1987-01-01	69.266
1988-01-01	69.747
1989-01-01	70.073
1990-01-01	70.250
1991-01-01	70.303
1992-01-01	70.283
1993-01-01	70.241
1994-01-01	70.204
1995-01-01	70.192
1996-01-01	70.214
1997-01-01	70.266
1998-01-01	70.346
1999-01-01	70.462
2000-01-01	70.624
2001-01-01	70.841
2002-01-01	71.110
2003-01-01	71.424
2004-01-01	71.775
2005-01-01	72.149
2006-01-01	72.534
2007-01-01	72.915
2008-01-01	73.279
2009-01-01	73.617
2010-01-01	73.923
2011-01-01	74.197
2012-01-01	74.446
2013-01-01	74.678
2014-01-01	74.895
2015-01-01	75.103
2016-01-01	75.303