Year	Number of Years
1960-01-01	33.251
1961-01-01	33.573
1962-01-01	33.914
1963-01-01	34.272
1964-01-01	34.645
1965-01-01	35.031
1966-01-01	35.426
1967-01-01	35.828
1968-01-01	36.234
1969-01-01	36.640
1970-01-01	37.047
1971-01-01	37.460
1972-01-01	37.878
1973-01-01	38.297
1974-01-01	38.712
1975-01-01	39.110
1976-01-01	39.478
1977-01-01	39.810
1978-01-01	40.099
1979-01-01	40.344
1980-01-01	40.546
1981-01-01	40.710
1982-01-01	40.848
1983-01-01	40.970
1984-01-01	41.085
1985-01-01	41.193
1986-01-01	41.292
1987-01-01	41.382
1988-01-01	41.471
1989-01-01	41.572
1990-01-01	41.696
1991-01-01	41.855
1992-01-01	42.060
1993-01-01	42.329
1994-01-01	42.677
1995-01-01	43.125
1996-01-01	43.695
1997-01-01	44.385
1998-01-01	45.192
1999-01-01	46.105
2000-01-01	47.113
2001-01-01	48.200
2002-01-01	49.341
2003-01-01	50.508
2004-01-01	51.676
2005-01-01	52.833
2006-01-01	53.974
2007-01-01	55.096
2008-01-01	56.189
2009-01-01	57.231
2010-01-01	58.192
2011-01-01	59.042
2012-01-01	59.770
2013-01-01	60.373
2014-01-01	60.858
2015-01-01	61.241
2016-01-01	61.547