Year	Number of Years
1960-01-01	48.458
1961-01-01	48.880
1962-01-01	49.307
1963-01-01	49.738
1964-01-01	50.168
1965-01-01	50.593
1966-01-01	51.009
1967-01-01	51.413
1968-01-01	51.808
1969-01-01	52.195
1970-01-01	52.572
1971-01-01	52.940
1972-01-01	53.305
1973-01-01	53.676
1974-01-01	54.066
1975-01-01	54.492
1976-01-01	54.976
1977-01-01	55.525
1978-01-01	56.141
1979-01-01	56.823
1980-01-01	57.560
1981-01-01	58.339
1982-01-01	59.139
1983-01-01	59.937
1984-01-01	60.717
1985-01-01	61.469
1986-01-01	62.189
1987-01-01	62.878
1988-01-01	63.536
1989-01-01	64.158
1990-01-01	64.733
1991-01-01	65.253
1992-01-01	65.716
1993-01-01	66.129
1994-01-01	66.502
1995-01-01	66.848
1996-01-01	67.184
1997-01-01	67.526
1998-01-01	67.889
1999-01-01	68.284
2000-01-01	68.722
2001-01-01	69.209
2002-01-01	69.738
2003-01-01	70.296
2004-01-01	70.873
2005-01-01	71.456
2006-01-01	72.029
2007-01-01	72.580
2008-01-01	73.097
2009-01-01	73.572
2010-01-01	73.999
2011-01-01	74.377
2012-01-01	74.717
2013-01-01	75.026
2014-01-01	75.309
2015-01-01	75.573
2016-01-01	75.821