Year	Number of Years
1960-01-01	48.022
1961-01-01	49.222
1962-01-01	50.409
1963-01-01	51.580
1964-01-01	52.730
1965-01-01	53.839
1966-01-01	54.885
1967-01-01	55.850
1968-01-01	56.723
1969-01-01	57.500
1970-01-01	58.199
1971-01-01	58.849
1972-01-01	59.470
1973-01-01	60.062
1974-01-01	60.611
1975-01-01	61.046
1976-01-01	61.276
1977-01-01	61.263
1978-01-01	61.018
1979-01-01	60.598
1980-01-01	60.127
1981-01-01	59.766
1982-01-01	59.647
1983-01-01	59.850
1984-01-01	60.393
1985-01-01	61.236
1986-01-01	62.285
1987-01-01	63.393
1988-01-01	64.436
1989-01-01	65.354
1990-01-01	66.118
1991-01-01	66.735
1992-01-01	67.256
1993-01-01	67.722
1994-01-01	68.134
1995-01-01	68.489
1996-01-01	68.776
1997-01-01	68.987
1998-01-01	69.122
1999-01-01	69.183
2000-01-01	69.169
2001-01-01	69.081
2002-01-01	68.932
2003-01-01	68.742
2004-01-01	68.537
2005-01-01	68.350
2006-01-01	68.217
2007-01-01	68.156
2008-01-01	68.177
2009-01-01	68.283
2010-01-01	68.465
2011-01-01	68.702
2012-01-01	68.963
2013-01-01	69.219
2014-01-01	69.458
2015-01-01	69.672
2016-01-01	69.862