Year	Number of Years
1960-01-01	44.285
1961-01-01	44.584
1962-01-01	44.871
1963-01-01	45.155
1964-01-01	45.446
1965-01-01	45.762
1966-01-01	46.118
1967-01-01	46.522
1968-01-01	46.979
1969-01-01	47.487
1970-01-01	48.041
1971-01-01	48.628
1972-01-01	49.232
1973-01-01	49.840
1974-01-01	50.448
1975-01-01	51.057
1976-01-01	51.674
1977-01-01	52.307
1978-01-01	52.963
1979-01-01	53.640
1980-01-01	54.348
1981-01-01	55.098
1982-01-01	55.881
1983-01-01	56.677
1984-01-01	57.460
1985-01-01	58.208
1986-01-01	58.900
1987-01-01	59.505
1988-01-01	59.983
1989-01-01	60.292
1990-01-01	60.369
1991-01-01	60.155
1992-01-01	59.639
1993-01-01	58.836
1994-01-01	57.771
1995-01-01	56.464
1996-01-01	54.942
1997-01-01	53.285
1998-01-01	51.594
1999-01-01	49.968
2000-01-01	48.521
2001-01-01	47.352
2002-01-01	46.508
2003-01-01	46.018
2004-01-01	45.905
2005-01-01	46.185
2006-01-01	46.846
2007-01-01	47.805
2008-01-01	48.969
2009-01-01	50.260
2010-01-01	51.598
2011-01-01	52.912
2012-01-01	54.158
2013-01-01	55.296
2014-01-01	56.287
2015-01-01	57.107
2016-01-01	57.754