Year	Number of Years
1960-01-01	54.471
1961-01-01	54.897
1962-01-01	55.326
1963-01-01	55.757
1964-01-01	56.186
1965-01-01	56.609
1966-01-01	57.021
1967-01-01	57.417
1968-01-01	57.794
1969-01-01	58.147
1970-01-01	58.472
1971-01-01	58.765
1972-01-01	59.028
1973-01-01	59.267
1974-01-01	59.488
1975-01-01	59.703
1976-01-01	59.925
1977-01-01	60.163
1978-01-01	60.422
1979-01-01	60.701
1980-01-01	60.999
1981-01-01	61.311
1982-01-01	61.622
1983-01-01	61.920
1984-01-01	62.193
1985-01-01	62.426
1986-01-01	62.605
1987-01-01	62.727
1988-01-01	62.797
1989-01-01	62.820
1990-01-01	62.811
1991-01-01	62.784
1992-01-01	62.761
1993-01-01	62.757
1994-01-01	62.785
1995-01-01	62.850
1996-01-01	62.952
1997-01-01	63.083
1998-01-01	63.237
1999-01-01	63.412
2000-01-01	63.613
2001-01-01	63.842
2002-01-01	64.101
2003-01-01	64.386
2004-01-01	64.693
2005-01-01	65.017
2006-01-01	65.354
2007-01-01	65.695
2008-01-01	66.031
2009-01-01	66.355
2010-01-01	66.657
2011-01-01	66.928
2012-01-01	67.167
2013-01-01	67.375
2014-01-01	67.552
2015-01-01	67.704
2016-01-01	67.835