Year	Percent of Total
1960-01-01	54.3270840308001
1961-01-01	54.1854053198942
1962-01-01	54.2906882934907
1963-01-01	54.4609850141114
1964-01-01	54.4937397172416
1965-01-01	54.3392221845289
1966-01-01	53.8993700454153
1967-01-01	53.4388151936498
1968-01-01	52.9687744728112
1969-01-01	52.5422484938654
1970-01-01	52.1874745551456
1971-01-01	51.7635736721536
1972-01-01	51.4562781770299
1973-01-01	51.2158389656186
1974-01-01	50.9584220761182
1975-01-01	50.6171297556014
1976-01-01	50.2526593604661
1977-01-01	50.0935205907474
1978-01-01	50.1535674398068
1979-01-01	50.5062707350819
1980-01-01	51.1809115221752
1981-01-01	51.2502100352859
1982-01-01	51.5725294662718
1983-01-01	52.0276687269237
1984-01-01	52.3635709834810
1985-01-01	52.3917267564666
1986-01-01	52.5606291032901
1987-01-01	52.4118450839231
1988-01-01	52.1437658672323
1989-01-01	52.0804662117106
1990-01-01	52.4017696536912
1991-01-01	52.3104784755225
1992-01-01	52.6015601882111
1993-01-01	53.1482065336017
1994-01-01	53.6828811342522
1995-01-01	54.0341821227561
1996-01-01	54.5466550253075
1997-01-01	54.8645667694980
1998-01-01	55.0973241729502
1999-01-01	55.4501577634020
2000-01-01	56.0165778501193
2001-01-01	56.3619216853575
2002-01-01	56.8985595420124
2003-01-01	57.5591044205559
2004-01-01	58.2217107448310
2005-01-01	58.8238298176582
2006-01-01	59.3828497076141
2007-01-01	59.9346183972859
2008-01-01	60.4698554197542
2009-01-01	60.9919458916878
2010-01-01	61.5007296045567
2011-01-01	62.0165208323469
2012-01-01	62.4876728496286
2013-01-01	62.9374988847849
2014-01-01	63.4019759604633
2015-01-01	63.8921776035298
2016-01-01	64.2700616448750
2017-01-01	64.7004916482494