Year	Number of Years
1960-01-01	36.975
1961-01-01	37.430
1962-01-01	37.870
1963-01-01	38.289
1964-01-01	38.689
1965-01-01	39.070
1966-01-01	39.439
1967-01-01	39.807
1968-01-01	40.182
1969-01-01	40.568
1970-01-01	40.970
1971-01-01	41.391
1972-01-01	41.827
1973-01-01	42.275
1974-01-01	42.728
1975-01-01	43.186
1976-01-01	43.646
1977-01-01	44.103
1978-01-01	44.546
1979-01-01	44.962
1980-01-01	45.331
1981-01-01	45.635
1982-01-01	45.866
1983-01-01	46.021
1984-01-01	46.104
1985-01-01	46.125
1986-01-01	46.099
1987-01-01	46.046
1988-01-01	45.988
1989-01-01	45.937
1990-01-01	45.898
1991-01-01	45.873
1992-01-01	45.855
1993-01-01	45.843
1994-01-01	45.841
1995-01-01	45.852
1996-01-01	45.877
1997-01-01	45.921
1998-01-01	45.992
1999-01-01	46.101
2000-01-01	46.266
2001-01-01	46.509
2002-01-01	46.834
2003-01-01	47.240
2004-01-01	47.717
2005-01-01	48.246
2006-01-01	48.802
2007-01-01	49.356
2008-01-01	49.887
2009-01-01	50.385
2010-01-01	50.847
2011-01-01	51.279
2012-01-01	51.699
2013-01-01	52.121
2014-01-01	52.549
2015-01-01	52.985
2016-01-01	53.428