Year	Number of Years
1960-01-01	50.661
1961-01-01	51.028
1962-01-01	51.381
1963-01-01	51.726
1964-01-01	52.068
1965-01-01	52.418
1966-01-01	52.787
1967-01-01	53.184
1968-01-01	53.617
1969-01-01	54.090
1970-01-01	54.609
1971-01-01	55.176
1972-01-01	55.782
1973-01-01	56.415
1974-01-01	57.065
1975-01-01	57.721
1976-01-01	58.375
1977-01-01	59.016
1978-01-01	59.630
1979-01-01	60.204
1980-01-01	60.733
1981-01-01	61.215
1982-01-01	61.650
1983-01-01	62.029
1984-01-01	62.334
1985-01-01	62.556
1986-01-01	62.688
1987-01-01	62.716
1988-01-01	62.620
1989-01-01	62.372
1990-01-01	61.905
1991-01-01	61.146
1992-01-01	60.083
1993-01-01	58.748
1994-01-01	57.203
1995-01-01	55.530
1996-01-01	53.826
1997-01-01	52.211
1998-01-01	50.808
1999-01-01	49.712
2000-01-01	49.030
2001-01-01	48.838
2002-01-01	49.108
2003-01-01	49.788
2004-01-01	50.832
2005-01-01	52.165
2006-01-01	53.695
2007-01-01	55.312
2008-01-01	56.919
2009-01-01	58.450
2010-01-01	59.868
2011-01-01	61.179
2012-01-01	62.425
2013-01-01	63.630
2014-01-01	64.780
2015-01-01	65.846
2016-01-01	66.797