Year	Number of Years
1960-01-01	33.729
1961-01-01	34.229
1962-01-01	34.730
1963-01-01	35.232
1964-01-01	35.734
1965-01-01	36.272
1966-01-01	36.894
1967-01-01	37.596
1968-01-01	38.335
1969-01-01	39.041
1970-01-01	39.528
1971-01-01	39.574
1972-01-01	39.085
1973-01-01	38.077
1974-01-01	36.659
1975-01-01	35.092
1976-01-01	33.714
1977-01-01	32.826
1978-01-01	32.628
1979-01-01	33.177
1980-01-01	34.419
1981-01-01	36.184
1982-01-01	38.174
1983-01-01	40.132
1984-01-01	41.932
1985-01-01	43.481
1986-01-01	44.749
1987-01-01	45.820
1988-01-01	46.773
1989-01-01	47.638
1990-01-01	48.469
1991-01-01	49.332
1992-01-01	50.273
1993-01-01	51.317
1994-01-01	52.467
1995-01-01	53.696
1996-01-01	54.954
1997-01-01	56.179
1998-01-01	57.325
1999-01-01	58.380
2000-01-01	59.360
2001-01-01	60.304
2002-01-01	61.251
2003-01-01	62.223
2004-01-01	63.209
2005-01-01	64.175
2006-01-01	65.068
2007-01-01	65.842
2008-01-01	66.472
2009-01-01	66.956
2010-01-01	67.313
2011-01-01	67.578
2012-01-01	67.805
2013-01-01	68.033
2014-01-01	68.285
2015-01-01	68.569
2016-01-01	68.881