Year	Number of Years
1960-01-01	44.947
1961-01-01	45.512
1962-01-01	46.070
1963-01-01	46.622
1964-01-01	47.173
1965-01-01	47.730
1966-01-01	48.300
1967-01-01	48.889
1968-01-01	49.505
1969-01-01	50.150
1970-01-01	50.856
1971-01-01	51.662
1972-01-01	52.561
1973-01-01	53.514
1974-01-01	54.463
1975-01-01	55.265
1976-01-01	55.744
1977-01-01	55.826
1978-01-01	55.513
1979-01-01	54.880
1980-01-01	54.111
1981-01-01	53.452
1982-01-01	53.128
1983-01-01	53.293
1984-01-01	53.995
1985-01-01	55.213
1986-01-01	56.846
1987-01-01	58.683
1988-01-01	60.528
1989-01-01	62.275
1990-01-01	63.828
1991-01-01	65.131
1992-01-01	66.209
1993-01-01	67.094
1994-01-01	67.791
1995-01-01	68.326
1996-01-01	68.741
1997-01-01	69.092
1998-01-01	69.428
1999-01-01	69.775
2000-01-01	70.144
2001-01-01	70.526
2002-01-01	70.899
2003-01-01	71.249
2004-01-01	71.582
2005-01-01	71.912
2006-01-01	72.259
2007-01-01	72.635
2008-01-01	73.044
2009-01-01	73.481
2010-01-01	73.932
2011-01-01	74.375
2012-01-01	74.787
2013-01-01	75.153
2014-01-01	75.466
2015-01-01	75.730
2016-01-01	75.953