Year	Number of Years
1960-01-01	31.697
1961-01-01	32.125
1962-01-01	32.550
1963-01-01	32.975
1964-01-01	33.402
1965-01-01	33.828
1966-01-01	34.248
1967-01-01	34.656
1968-01-01	35.051
1969-01-01	35.432
1970-01-01	35.807
1971-01-01	36.186
1972-01-01	36.575
1973-01-01	36.974
1974-01-01	37.378
1975-01-01	37.767
1976-01-01	38.118
1977-01-01	38.417
1978-01-01	38.662
1979-01-01	38.861
1980-01-01	39.033
1981-01-01	39.206
1982-01-01	39.410
1983-01-01	39.671
1984-01-01	40.005
1985-01-01	40.423
1986-01-01	40.931
1987-01-01	41.513
1988-01-01	42.149
1989-01-01	42.825
1990-01-01	43.525
1991-01-01	44.232
1992-01-01	44.933
1993-01-01	45.612
1994-01-01	46.258
1995-01-01	46.859
1996-01-01	47.409
1997-01-01	47.916
1998-01-01	48.386
1999-01-01	48.825
2000-01-01	49.239
2001-01-01	49.631
2002-01-01	50.013
2003-01-01	50.393
2004-01-01	50.782
2005-01-01	51.190
2006-01-01	51.627
2007-01-01	52.095
2008-01-01	52.591
2009-01-01	53.113
2010-01-01	53.655
2011-01-01	54.206
2012-01-01	54.756
2013-01-01	55.294
2014-01-01	55.817
2015-01-01	56.322
2016-01-01	56.811