Year	Number of Years
1960-01-01	60.556
1961-01-01	61.269
1962-01-01	61.964
1963-01-01	62.630
1964-01-01	63.259
1965-01-01	63.848
1966-01-01	64.399
1967-01-01	64.924
1968-01-01	65.434
1969-01-01	65.937
1970-01-01	66.439
1971-01-01	66.946
1972-01-01	67.460
1973-01-01	67.983
1974-01-01	68.519
1975-01-01	69.072
1976-01-01	69.648
1977-01-01	70.242
1978-01-01	70.846
1979-01-01	71.452
1980-01-01	72.045
1981-01-01	72.610
1982-01-01	73.135
1983-01-01	73.612
1984-01-01	74.035
1985-01-01	74.401
1986-01-01	74.714
1987-01-01	74.984
1988-01-01	75.223
1989-01-01	75.438
1990-01-01	75.638
1991-01-01	75.830
1992-01-01	76.016
1993-01-01	76.200
1994-01-01	76.385
1995-01-01	76.571
1996-01-01	76.759
1997-01-01	76.942
1998-01-01	77.119
1999-01-01	77.288
2000-01-01	77.448
2001-01-01	77.597
2002-01-01	77.736
2003-01-01	77.868
2004-01-01	77.993
2005-01-01	78.114
2006-01-01	78.234
2007-01-01	78.355
2008-01-01	78.481
2009-01-01	78.613
2010-01-01	78.756
2011-01-01	78.911
2012-01-01	79.077
2013-01-01	79.254
2014-01-01	79.440
2015-01-01	79.634
2016-01-01	79.831