Year	Number of Years
1960-01-01	46.602
1961-01-01	47.089
1962-01-01	47.501
1963-01-01	47.829
1964-01-01	48.080
1965-01-01	48.264
1966-01-01	48.401
1967-01-01	48.522
1968-01-01	48.656
1969-01-01	48.822
1970-01-01	49.037
1971-01-01	49.309
1972-01-01	49.634
1973-01-01	50.006
1974-01-01	50.426
1975-01-01	50.896
1976-01-01	51.418
1977-01-01	51.985
1978-01-01	52.582
1979-01-01	53.196
1980-01-01	53.807
1981-01-01	54.396
1982-01-01	54.949
1983-01-01	55.462
1984-01-01	55.931
1985-01-01	56.395
1986-01-01	56.905
1987-01-01	57.480
1988-01-01	58.098
1989-01-01	58.708
1990-01-01	59.206
1991-01-01	59.464
1992-01-01	59.394
1993-01-01	58.944
1994-01-01	58.112
1995-01-01	56.902
1996-01-01	55.351
1997-01-01	53.584
1998-01-01	51.750
1999-01-01	49.971
2000-01-01	48.405
2001-01-01	47.195
2002-01-01	46.394
2003-01-01	46.021
2004-01-01	46.078
2005-01-01	46.521
2006-01-01	47.266
2007-01-01	48.171
2008-01-01	49.112
2009-01-01	50.014
2010-01-01	50.826
2011-01-01	51.530
2012-01-01	52.158
2013-01-01	52.738
2014-01-01	53.268
2015-01-01	53.745
2016-01-01	54.174