Year	Number of Years
1960-01-01	41.546
1961-01-01	41.988
1962-01-01	42.429
1963-01-01	42.868
1964-01-01	43.304
1965-01-01	43.741
1966-01-01	44.184
1967-01-01	44.640
1968-01-01	45.111
1969-01-01	45.598
1970-01-01	46.104
1971-01-01	46.627
1972-01-01	47.163
1973-01-01	47.705
1974-01-01	48.247
1975-01-01	48.784
1976-01-01	49.311
1977-01-01	49.825
1978-01-01	50.318
1979-01-01	50.781
1980-01-01	51.211
1981-01-01	51.604
1982-01-01	51.958
1983-01-01	52.266
1984-01-01	52.518
1985-01-01	52.698
1986-01-01	52.787
1987-01-01	52.781
1988-01-01	52.680
1989-01-01	52.490
1990-01-01	52.209
1991-01-01	51.835
1992-01-01	51.390
1993-01-01	50.910
1994-01-01	50.433
1995-01-01	50.015
1996-01-01	49.708
1997-01-01	49.543
1998-01-01	49.538
1999-01-01	49.700
2000-01-01	50.026
2001-01-01	50.495
2002-01-01	51.059
2003-01-01	51.671
2004-01-01	52.301
2005-01-01	52.916
2006-01-01	53.494
2007-01-01	54.033
2008-01-01	54.535
2009-01-01	54.996
2010-01-01	55.424
2011-01-01	55.832
2012-01-01	56.241
2013-01-01	56.665
2014-01-01	57.111
2015-01-01	57.582
2016-01-01	58.073