Year	Number of Years
1960-01-01	47.694
1961-01-01	48.235
1962-01-01	48.754
1963-01-01	49.249
1964-01-01	49.728
1965-01-01	50.214
1966-01-01	50.737
1967-01-01	51.319
1968-01-01	51.971
1969-01-01	52.690
1970-01-01	53.457
1971-01-01	54.245
1972-01-01	55.022
1973-01-01	55.762
1974-01-01	56.454
1975-01-01	57.099
1976-01-01	57.706
1977-01-01	58.295
1978-01-01	58.881
1979-01-01	59.471
1980-01-01	60.065
1981-01-01	60.662
1982-01-01	61.254
1983-01-01	61.836
1984-01-01	62.406
1985-01-01	62.962
1986-01-01	63.503
1987-01-01	64.029
1988-01-01	64.542
1989-01-01	65.045
1990-01-01	65.541
1991-01-01	66.034
1992-01-01	66.528
1993-01-01	67.024
1994-01-01	67.523
1995-01-01	68.026
1996-01-01	68.533
1997-01-01	69.041
1998-01-01	69.544
1999-01-01	70.036
2000-01-01	70.512
2001-01-01	70.964
2002-01-01	71.389
2003-01-01	71.784
2004-01-01	72.146
2005-01-01	72.473
2006-01-01	72.764
2007-01-01	73.023
2008-01-01	73.258
2009-01-01	73.475
2010-01-01	73.681
2011-01-01	73.883
2012-01-01	74.088
2013-01-01	74.298
2014-01-01	74.518
2015-01-01	74.747
2016-01-01	74.983