Year	Number of Years
1960-01-01	41.281
1961-01-01	41.592
1962-01-01	41.907
1963-01-01	42.225
1964-01-01	42.540
1965-01-01	42.838
1966-01-01	43.103
1967-01-01	43.328
1968-01-01	43.515
1969-01-01	43.675
1970-01-01	43.829
1971-01-01	44.006
1972-01-01	44.232
1973-01-01	44.517
1974-01-01	44.865
1975-01-01	45.266
1976-01-01	45.701
1977-01-01	46.141
1978-01-01	46.562
1979-01-01	46.953
1980-01-01	47.314
1981-01-01	47.657
1982-01-01	47.992
1983-01-01	48.317
1984-01-01	48.618
1985-01-01	48.845
1986-01-01	48.941
1987-01-01	48.884
1988-01-01	48.684
1989-01-01	48.379
1990-01-01	48.053
1991-01-01	47.816
1992-01-01	47.752
1993-01-01	47.911
1994-01-01	48.295
1995-01-01	48.860
1996-01-01	49.526
1997-01-01	50.186
1998-01-01	50.758
1999-01-01	51.213
2000-01-01	51.545
2001-01-01	51.779
2002-01-01	51.977
2003-01-01	52.190
2004-01-01	52.437
2005-01-01	52.735
2006-01-01	53.090
2007-01-01	53.492
2008-01-01	53.926
2009-01-01	54.386
2010-01-01	54.861
2011-01-01	55.338
2012-01-01	55.807
2013-01-01	56.259
2014-01-01	56.688
2015-01-01	57.094
2016-01-01	57.481