Year	Percent of Total
1960-01-01	54.9971186476853
1961-01-01	54.1164496770781
1962-01-01	53.4628564148959
1963-01-01	53.0231640253661
1964-01-01	52.7676482682035
1965-01-01	52.6939614238761
1966-01-01	52.8086831857739
1967-01-01	53.1498116388870
1968-01-01	53.6866655005539
1969-01-01	54.3562633860146
1970-01-01	55.1051953118038
1971-01-01	56.1382552732034
1972-01-01	57.0919499985663
1973-01-01	58.0044242421338
1974-01-01	58.9440925938811
1975-01-01	59.9321791456168
1976-01-01	60.7161112397342
1977-01-01	61.5814404327704
1978-01-01	62.4405195016633
1979-01-01	63.1835571421778
1980-01-01	63.7703802660278
1981-01-01	64.1888483564013
1982-01-01	64.4436866993186
1983-01-01	64.5749359135477
1984-01-01	64.6516384399173
1985-01-01	64.7046779988219
1986-01-01	64.7275146687043
1987-01-01	64.7159193288879
1988-01-01	64.6418145487240
1989-01-01	64.4965925051230
1990-01-01	64.3241623836085
1991-01-01	63.8981060129503
1992-01-01	63.4442214353972
1993-01-01	63.0062222391379
1994-01-01	62.6365397148304
1995-01-01	62.3613529428951
1996-01-01	62.5014085218333
1997-01-01	62.8136284800353
1998-01-01	63.2515881318268
1999-01-01	63.7277166166453
2000-01-01	64.1732050034076
2001-01-01	64.7610431202480
2002-01-01	65.2077179943815
2003-01-01	65.5930831869245
2004-01-01	66.0468931004742
2005-01-01	66.6387589941028
2006-01-01	67.1655230691229
2007-01-01	67.8524719609854
2008-01-01	68.5851139184794
2009-01-01	69.1860787153844
2010-01-01	69.5456625995591
2011-01-01	69.7065045289978
2012-01-01	69.7222894998546
2013-01-01	69.6111883529652
2014-01-01	69.4364156877318
2015-01-01	69.2461989406743
2016-01-01	69.0155209763623
2017-01-01	68.7608729034790