Year	Number of Years
1960-01-01	64.387
1961-01-01	64.960
1962-01-01	65.484
1963-01-01	65.962
1964-01-01	66.396
1965-01-01	66.789
1966-01-01	67.144
1967-01-01	67.466
1968-01-01	67.763
1969-01-01	68.045
1970-01-01	68.324
1971-01-01	68.609
1972-01-01	68.907
1973-01-01	69.219
1974-01-01	69.546
1975-01-01	69.885
1976-01-01	70.235
1977-01-01	70.583
1978-01-01	70.919
1979-01-01	71.231
1980-01-01	71.509
1981-01-01	71.739
1982-01-01	71.920
1983-01-01	72.052
1984-01-01	72.135
1985-01-01	72.175
1986-01-01	72.179
1987-01-01	72.160
1988-01-01	72.129
1989-01-01	72.096
1990-01-01	72.065
1991-01-01	72.039
1992-01-01	72.015
1993-01-01	71.996
1994-01-01	71.986
1995-01-01	71.990
1996-01-01	72.011
1997-01-01	72.052
1998-01-01	72.116
1999-01-01	72.205
2000-01-01	72.327
2001-01-01	72.487
2002-01-01	72.683
2003-01-01	72.911
2004-01-01	73.167
2005-01-01	73.446
2006-01-01	73.739
2007-01-01	74.038
2008-01-01	74.334
2009-01-01	74.619
2010-01-01	74.883
2011-01-01	75.122
2012-01-01	75.334
2013-01-01	75.523
2014-01-01	75.689
2015-01-01	75.836
2016-01-01	75.970