Year	Number of Years
1960-01-01	42.138
1961-01-01	42.454
1962-01-01	42.778
1963-01-01	43.110
1964-01-01	43.451
1965-01-01	43.800
1966-01-01	44.157
1967-01-01	44.523
1968-01-01	44.898
1969-01-01	45.280
1970-01-01	45.671
1971-01-01	46.070
1972-01-01	46.477
1973-01-01	46.892
1974-01-01	47.315
1975-01-01	47.745
1976-01-01	48.183
1977-01-01	48.629
1978-01-01	49.082
1979-01-01	49.543
1980-01-01	50.012
1981-01-01	50.489
1982-01-01	50.974
1983-01-01	51.466
1984-01-01	51.965
1985-01-01	52.472
1986-01-01	52.986
1987-01-01	53.507
1988-01-01	54.034
1989-01-01	54.566
1990-01-01	55.104
1991-01-01	55.647
1992-01-01	56.195
1993-01-01	56.747
1994-01-01	57.303
1995-01-01	57.862
1996-01-01	58.423
1997-01-01	58.987
1998-01-01	59.554
1999-01-01	60.122
2000-01-01	60.690
2001-01-01	61.260
2002-01-01	61.829
2003-01-01	62.399
2004-01-01	62.968
2005-01-01	63.538
2006-01-01	64.113
2007-01-01	64.692
2008-01-01	65.272
2009-01-01	65.847
2010-01-01	66.408
2011-01-01	66.945
2012-01-01	67.451
2013-01-01	67.922
2014-01-01	68.357
2015-01-01	68.756
2016-01-01	69.125