Year	Number of Years
1960-01-01	51.971
1961-01-01	52.568
1962-01-01	53.176
1963-01-01	53.797
1964-01-01	54.435
1965-01-01	55.096
1966-01-01	55.788
1967-01-01	56.510
1968-01-01	57.260
1969-01-01	58.030
1970-01-01	58.814
1971-01-01	59.600
1972-01-01	60.378
1973-01-01	61.137
1974-01-01	61.872
1975-01-01	62.579
1976-01-01	63.258
1977-01-01	63.914
1978-01-01	64.552
1979-01-01	65.172
1980-01-01	65.774
1981-01-01	66.359
1982-01-01	66.928
1983-01-01	67.477
1984-01-01	68.005
1985-01-01	68.508
1986-01-01	68.981
1987-01-01	69.423
1988-01-01	69.831
1989-01-01	70.207
1990-01-01	70.553
1991-01-01	70.871
1992-01-01	71.167
1993-01-01	71.444
1994-01-01	71.708
1995-01-01	71.961
1996-01-01	72.205
1997-01-01	72.439
1998-01-01	72.664
1999-01-01	72.882
2000-01-01	73.110
2001-01-01	73.371
2002-01-01	73.663
2003-01-01	73.967
2004-01-01	74.250
2005-01-01	74.430
2006-01-01	74.412
2007-01-01	74.152
2008-01-01	73.648
2009-01-01	72.939
2010-01-01	72.108
2011-01-01	71.270
2012-01-01	70.549
2013-01-01	70.046
2014-01-01	69.817
2015-01-01	69.904
2016-01-01	70.310