Year	Percent of Total
1960-01-01	52.5903724998471
1961-01-01	52.0211224823590
1962-01-01	51.2712811117566
1963-01-01	50.5300504402838
1964-01-01	50.0694955441092
1965-01-01	49.9829143275568
1966-01-01	50.3941630325394
1967-01-01	51.1111703735310
1968-01-01	51.9847392963120
1969-01-01	52.8114966883133
1970-01-01	53.4915845442689
1971-01-01	54.1524836803560
1972-01-01	54.6514819846135
1973-01-01	55.0585621970921
1974-01-01	55.4867867112805
1975-01-01	55.9896332675619
1976-01-01	56.1667776298269
1977-01-01	56.6048531523748
1978-01-01	57.1580683780488
1979-01-01	57.7087862898069
1980-01-01	58.2318032059975
1981-01-01	58.4306669665392
1982-01-01	58.5665217728790
1983-01-01	58.6802805747257
1984-01-01	58.8277344233298
1985-01-01	59.0409421322691
1986-01-01	59.9133228270093
1987-01-01	60.7696257080573
1988-01-01	61.5389964738319
1989-01-01	62.1885859236464
1990-01-01	62.7258148656220
1991-01-01	62.9633385159648
1992-01-01	63.2242310092969
1993-01-01	63.4968465063123
1994-01-01	63.8072705293153
1995-01-01	64.1871248216641
1996-01-01	64.5745473401619
1997-01-01	65.0754074824220
1998-01-01	65.6539962784520
1999-01-01	66.2844901299155
2000-01-01	66.9551465756014
2001-01-01	67.3744623173790
2002-01-01	67.8657814090127
2003-01-01	68.3388560481509
2004-01-01	68.7758502237687
2005-01-01	69.2010034012674
2006-01-01	69.4014854827819
2007-01-01	69.6935421913014
2008-01-01	70.0196702983768
2009-01-01	70.3349905673160
2010-01-01	70.6405565761510
2011-01-01	71.0908015725369
2012-01-01	71.4512642965068
2013-01-01	71.7464926204537
2014-01-01	72.0061014709597
2015-01-01	72.2382419014135
2016-01-01	72.2901445193244
2017-01-01	72.3849245504401