Year	Number of Years
1960-01-01	49.174
1961-01-01	49.679
1962-01-01	50.183
1963-01-01	50.688
1964-01-01	51.194
1965-01-01	51.701
1966-01-01	52.208
1967-01-01	52.717
1968-01-01	53.227
1969-01-01	53.737
1970-01-01	54.252
1971-01-01	54.780
1972-01-01	55.319
1973-01-01	55.862
1974-01-01	56.398
1975-01-01	56.919
1976-01-01	57.417
1977-01-01	57.876
1978-01-01	58.276
1979-01-01	58.594
1980-01-01	58.778
1981-01-01	58.774
1982-01-01	58.574
1983-01-01	58.203
1984-01-01	57.705
1985-01-01	57.162
1986-01-01	56.677
1987-01-01	56.337
1988-01-01	56.204
1989-01-01	56.306
1990-01-01	56.638
1991-01-01	57.162
1992-01-01	57.796
1993-01-01	58.471
1994-01-01	59.153
1995-01-01	59.822
1996-01-01	60.475
1997-01-01	61.127
1998-01-01	61.788
1999-01-01	62.449
2000-01-01	63.103
2001-01-01	63.744
2002-01-01	64.368
2003-01-01	64.971
2004-01-01	65.549
2005-01-01	66.104
2006-01-01	66.635
2007-01-01	67.147
2008-01-01	67.641
2009-01-01	68.118
2010-01-01	68.572
2011-01-01	69.001
2012-01-01	69.400
2013-01-01	69.771
2014-01-01	70.113
2015-01-01	70.430
2016-01-01	70.726