Year	Number of Years
1960-01-01	48.392
1961-01-01	49.304
1962-01-01	50.185
1963-01-01	51.012
1964-01-01	51.771
1965-01-01	52.461
1966-01-01	53.098
1967-01-01	53.702
1968-01-01	54.285
1969-01-01	54.845
1970-01-01	55.364
1971-01-01	55.819
1972-01-01	56.192
1973-01-01	56.477
1974-01-01	56.676
1975-01-01	56.796
1976-01-01	56.848
1977-01-01	56.860
1978-01-01	56.861
1979-01-01	56.875
1980-01-01	56.936
1981-01-01	57.074
1982-01-01	57.295
1983-01-01	57.595
1984-01-01	57.968
1985-01-01	58.392
1986-01-01	58.836
1987-01-01	59.266
1988-01-01	59.655
1989-01-01	59.992
1990-01-01	60.268
1991-01-01	60.486
1992-01-01	60.670
1993-01-01	60.841
1994-01-01	61.015
1995-01-01	61.211
1996-01-01	61.447
1997-01-01	61.730
1998-01-01	62.063
1999-01-01	62.446
2000-01-01	62.869
2001-01-01	63.319
2002-01-01	63.777
2003-01-01	64.230
2004-01-01	64.671
2005-01-01	65.104
2006-01-01	65.539
2007-01-01	65.987
2008-01-01	66.449
2009-01-01	66.920
2010-01-01	67.383
2011-01-01	67.820
2012-01-01	68.215
2013-01-01	68.558
2014-01-01	68.847
2015-01-01	69.087
2016-01-01	69.287