Year	Number of Years
1960-01-01	36.977
1961-01-01	37.375
1962-01-01	37.774
1963-01-01	38.176
1964-01-01	38.579
1965-01-01	38.982
1966-01-01	39.384
1967-01-01	39.784
1968-01-01	40.179
1969-01-01	40.571
1970-01-01	40.958
1971-01-01	41.344
1972-01-01	41.728
1973-01-01	42.112
1974-01-01	42.495
1975-01-01	42.877
1976-01-01	43.259
1977-01-01	43.639
1978-01-01	44.012
1979-01-01	44.374
1980-01-01	44.724
1981-01-01	45.065
1982-01-01	45.391
1983-01-01	45.693
1984-01-01	45.957
1985-01-01	46.142
1986-01-01	46.196
1987-01-01	46.111
1988-01-01	45.908
1989-01-01	45.631
1990-01-01	45.375
1991-01-01	45.258
1992-01-01	45.359
1993-01-01	45.720
1994-01-01	46.335
1995-01-01	47.148
1996-01-01	48.065
1997-01-01	48.963
1998-01-01	49.751
1999-01-01	50.389
2000-01-01	50.867
2001-01-01	51.211
2002-01-01	51.490
2003-01-01	51.761
2004-01-01	52.042
2005-01-01	52.344
2006-01-01	52.666
2007-01-01	52.996
2008-01-01	53.323
2009-01-01	53.652
2010-01-01	53.986
2011-01-01	54.332
2012-01-01	54.694
2013-01-01	55.072
2014-01-01	55.467
2015-01-01	55.876
2016-01-01	56.293