Year	Number of Years
1960-01-01	37.271
1961-01-01	37.727
1962-01-01	38.188
1963-01-01	38.655
1964-01-01	39.130
1965-01-01	39.615
1966-01-01	40.109
1967-01-01	40.610
1968-01-01	41.117
1969-01-01	41.630
1970-01-01	42.152
1971-01-01	42.684
1972-01-01	43.229
1973-01-01	43.781
1974-01-01	44.337
1975-01-01	44.882
1976-01-01	45.399
1977-01-01	45.883
1978-01-01	46.335
1979-01-01	46.764
1980-01-01	47.190
1981-01-01	47.643
1982-01-01	48.145
1983-01-01	48.710
1984-01-01	49.339
1985-01-01	50.034
1986-01-01	50.790
1987-01-01	51.581
1988-01-01	52.372
1989-01-01	53.132
1990-01-01	53.812
1991-01-01	54.366
1992-01-01	54.776
1993-01-01	55.042
1994-01-01	55.174
1995-01-01	55.203
1996-01-01	55.170
1997-01-01	55.133
1998-01-01	55.139
1999-01-01	55.218
2000-01-01	55.391
2001-01-01	55.668
2002-01-01	56.025
2003-01-01	56.436
2004-01-01	56.887
2005-01-01	57.355
2006-01-01	57.817
2007-01-01	58.255
2008-01-01	58.654
2009-01-01	59.009
2010-01-01	59.319
2011-01-01	59.595
2012-01-01	59.855
2013-01-01	60.113
2014-01-01	60.373
2015-01-01	60.639
2016-01-01	60.907