Year	Number of Years
1960-01-01	69.618
1961-01-01	69.949
1962-01-01	70.272
1963-01-01	70.587
1964-01-01	70.895
1965-01-01	71.197
1966-01-01	71.491
1967-01-01	71.776
1968-01-01	72.052
1969-01-01	72.318
1970-01-01	72.576
1971-01-01	72.825
1972-01-01	73.067
1973-01-01	73.301
1974-01-01	73.530
1975-01-01	73.753
1976-01-01	73.971
1977-01-01	74.183
1978-01-01	74.390
1979-01-01	74.592
1980-01-01	74.790
1981-01-01	74.984
1982-01-01	75.174
1983-01-01	75.359
1984-01-01	75.541
1985-01-01	75.718
1986-01-01	75.892
1987-01-01	76.063
1988-01-01	76.230
1989-01-01	76.393
1990-01-01	76.554
1991-01-01	76.711
1992-01-01	76.865
1993-01-01	77.017
1994-01-01	77.166
1995-01-01	77.312
1996-01-01	77.456
1997-01-01	77.598
1998-01-01	77.738
1999-01-01	77.876
2000-01-01	78.010
2001-01-01	78.140
2002-01-01	78.264
2003-01-01	78.386
2004-01-01	78.506
2005-01-01	78.631
2006-01-01	78.764
2007-01-01	78.911
2008-01-01	79.071
2009-01-01	79.245
2010-01-01	79.430
2011-01-01	79.620
2012-01-01	79.810
2013-01-01	79.995
2014-01-01	80.173
2015-01-01	80.344
2016-01-01	80.508