Year	Number of Years
1960-01-01	61.995
1961-01-01	62.367
1962-01-01	62.743
1963-01-01	63.122
1964-01-01	63.496
1965-01-01	63.856
1966-01-01	64.186
1967-01-01	64.476
1968-01-01	64.718
1969-01-01	64.908
1970-01-01	65.045
1971-01-01	65.134
1972-01-01	65.186
1973-01-01	65.213
1974-01-01	65.221
1975-01-01	65.209
1976-01-01	65.172
1977-01-01	65.111
1978-01-01	65.037
1979-01-01	64.971
1980-01-01	64.951
1981-01-01	65.022
1982-01-01	65.205
1983-01-01	65.499
1984-01-01	65.887
1985-01-01	66.330
1986-01-01	66.772
1987-01-01	67.156
1988-01-01	67.440
1989-01-01	67.605
1990-01-01	67.643
1991-01-01	67.563
1992-01-01	67.408
1993-01-01	67.221
1994-01-01	67.030
1995-01-01	66.867
1996-01-01	66.761
1997-01-01	66.722
1998-01-01	66.752
1999-01-01	66.852
2000-01-01	67.006
2001-01-01	67.185
2002-01-01	67.362
2003-01-01	67.521
2004-01-01	67.665
2005-01-01	67.820
2006-01-01	68.022
2007-01-01	68.302
2008-01-01	68.671
2009-01-01	69.119
2010-01-01	69.616
2011-01-01	70.117
2012-01-01	70.577
2013-01-01	70.961
2014-01-01	71.258
2015-01-01	71.468
2016-01-01	71.610