Year	Number of Years
1960-01-01	43.725
1961-01-01	44.051
1962-01-01	44.783
1963-01-01	45.972
1964-01-01	47.592
1965-01-01	49.549
1966-01-01	51.696
1967-01-01	53.847
1968-01-01	55.843
1969-01-01	57.603
1970-01-01	59.085
1971-01-01	60.303
1972-01-01	61.344
1973-01-01	62.281
1974-01-01	63.134
1975-01-01	63.915
1976-01-01	64.631
1977-01-01	65.278
1978-01-01	65.857
1979-01-01	66.377
1980-01-01	66.843
1981-01-01	67.256
1982-01-01	67.618
1983-01-01	67.933
1984-01-01	68.210
1985-01-01	68.451
1986-01-01	68.661
1987-01-01	68.842
1988-01-01	69.002
1989-01-01	69.150
1990-01-01	69.293
1991-01-01	69.437
1992-01-01	69.587
1993-01-01	69.750
1994-01-01	69.935
1995-01-01	70.156
1996-01-01	70.427
1997-01-01	70.747
1998-01-01	71.115
1999-01-01	71.521
2000-01-01	71.955
2001-01-01	72.401
2002-01-01	72.840
2003-01-01	73.257
2004-01-01	73.642
2005-01-01	73.987
2006-01-01	74.291
2007-01-01	74.562
2008-01-01	74.808
2009-01-01	75.032
2010-01-01	75.236
2011-01-01	75.425
2012-01-01	75.602
2013-01-01	75.769
2014-01-01	75.932
2015-01-01	76.092
2016-01-01	76.252