Year	Percent of Total
1960-01-01	55.7154906511848
1961-01-01	54.6344717500328
1962-01-01	53.7644966039828
1963-01-01	52.9067025934658
1964-01-01	52.0266612717142
1965-01-01	51.2892744529987
1966-01-01	51.7186359370112
1967-01-01	52.0766284306575
1968-01-01	52.3281485948379
1969-01-01	52.5210756977912
1970-01-01	52.6981961854142
1971-01-01	53.5703910817386
1972-01-01	54.7446051799001
1973-01-01	56.0158145010792
1974-01-01	57.1626487132360
1975-01-01	58.0765580037743
1976-01-01	59.4861005384984
1977-01-01	60.6699101179187
1978-01-01	61.6530591424941
1979-01-01	62.5298280620074
1980-01-01	63.3633241452897
1981-01-01	63.6458890195659
1982-01-01	63.7862417411582
1983-01-01	63.8265725657958
1984-01-01	63.8199333541244
1985-01-01	63.8111246215102
1986-01-01	63.9094587549195
1987-01-01	64.1535237085526
1988-01-01	64.4345897051173
1989-01-01	64.7394458417344
1990-01-01	65.1274068368382
1991-01-01	65.3142134120624
1992-01-01	65.7085723789733
1993-01-01	66.2397219015578
1994-01-01	66.8206001586643
1995-01-01	67.3527893432488
1996-01-01	67.4604436395308
1997-01-01	67.6247625771099
1998-01-01	67.6794274745724
1999-01-01	67.5843813084699
2000-01-01	67.4057422804816
2001-01-01	68.5442886449554
2002-01-01	69.6091127228803
2003-01-01	70.5417028910597
2004-01-01	71.3518620277448
2005-01-01	72.0754683029529
2006-01-01	73.6306022240910
2007-01-01	74.9341388234863
2008-01-01	75.9944912479028
2009-01-01	76.8689205074306
2010-01-01	77.6087107188390
2011-01-01	77.5050478420426
2012-01-01	77.4051562162316
2013-01-01	77.2492399713854
2014-01-01	77.0372127444165
2015-01-01	76.8259765062634
2016-01-01	77.3655231547653
2017-01-01	77.9061680950620