Year	Number of Years
1960-01-01	36.489
1961-01-01	36.902
1962-01-01	37.326
1963-01-01	37.768
1964-01-01	38.233
1965-01-01	38.734
1966-01-01	39.281
1967-01-01	39.877
1968-01-01	40.522
1969-01-01	41.212
1970-01-01	41.946
1971-01-01	42.720
1972-01-01	43.521
1973-01-01	44.330
1974-01-01	45.129
1975-01-01	45.900
1976-01-01	46.628
1977-01-01	47.302
1978-01-01	47.911
1979-01-01	48.442
1980-01-01	48.886
1981-01-01	49.240
1982-01-01	49.507
1983-01-01	49.694
1984-01-01	49.799
1985-01-01	49.823
1986-01-01	49.761
1987-01-01	49.619
1988-01-01	49.402
1989-01-01	49.118
1990-01-01	48.767
1991-01-01	48.350
1992-01-01	47.873
1993-01-01	47.352
1994-01-01	46.807
1995-01-01	46.252
1996-01-01	45.700
1997-01-01	45.166
1998-01-01	44.675
1999-01-01	44.254
2000-01-01	43.937
2001-01-01	43.755
2002-01-01	43.718
2003-01-01	43.827
2004-01-01	44.080
2005-01-01	44.466
2006-01-01	44.967
2007-01-01	45.552
2008-01-01	46.190
2009-01-01	46.862
2010-01-01	47.560
2011-01-01	48.284
2012-01-01	49.041
2013-01-01	49.825
2014-01-01	50.621
2015-01-01	51.410
2016-01-01	52.171