Year	Number of Years
1960-01-01	39.587
1961-01-01	39.946
1962-01-01	40.392
1963-01-01	40.944
1964-01-01	41.606
1965-01-01	42.367
1966-01-01	43.204
1967-01-01	44.082
1968-01-01	44.966
1969-01-01	45.842
1970-01-01	46.698
1971-01-01	47.535
1972-01-01	48.363
1973-01-01	49.190
1974-01-01	50.018
1975-01-01	50.846
1976-01-01	51.676
1977-01-01	52.510
1978-01-01	53.344
1979-01-01	54.177
1980-01-01	55.014
1981-01-01	55.864
1982-01-01	56.722
1983-01-01	57.574
1984-01-01	58.398
1985-01-01	59.162
1986-01-01	59.832
1987-01-01	60.382
1988-01-01	60.798
1989-01-01	61.075
1990-01-01	61.215
1991-01-01	61.230
1992-01-01	61.152
1993-01-01	61.012
1994-01-01	60.832
1995-01-01	60.619
1996-01-01	60.372
1997-01-01	60.095
1998-01-01	59.804
1999-01-01	59.527
2000-01-01	59.302
2001-01-01	59.171
2002-01-01	59.154
2003-01-01	59.266
2004-01-01	59.512
2005-01-01	59.890
2006-01-01	60.388
2007-01-01	60.969
2008-01-01	61.597
2009-01-01	62.247
2010-01-01	62.893
2011-01-01	63.519
2012-01-01	64.119
2013-01-01	64.686
2014-01-01	65.211
2015-01-01	65.685
2016-01-01	66.105