Year	Number of Years
1960-01-01	51.868
1961-01-01	53.234
1962-01-01	54.589
1963-01-01	55.910
1964-01-01	57.181
1965-01-01	58.387
1966-01-01	59.523
1967-01-01	60.595
1968-01-01	61.608
1969-01-01	62.559
1970-01-01	63.448
1971-01-01	64.274
1972-01-01	65.042
1973-01-01	65.757
1974-01-01	66.421
1975-01-01	67.040
1976-01-01	67.616
1977-01-01	68.152
1978-01-01	68.651
1979-01-01	69.117
1980-01-01	69.550
1981-01-01	69.950
1982-01-01	70.316
1983-01-01	70.650
1984-01-01	70.956
1985-01-01	71.237
1986-01-01	71.495
1987-01-01	71.735
1988-01-01	71.962
1989-01-01	72.179
1990-01-01	72.390
1991-01-01	72.598
1992-01-01	72.803
1993-01-01	73.006
1994-01-01	73.209
1995-01-01	73.413
1996-01-01	73.619
1997-01-01	73.826
1998-01-01	74.033
1999-01-01	74.239
2000-01-01	74.440
2001-01-01	74.635
2002-01-01	74.822
2003-01-01	74.999
2004-01-01	75.167
2005-01-01	75.326
2006-01-01	75.478
2007-01-01	75.625
2008-01-01	75.770
2009-01-01	75.913
2010-01-01	76.056
2011-01-01	76.199
2012-01-01	76.341
2013-01-01	76.482
2014-01-01	76.622
2015-01-01	76.761
2016-01-01	76.900