Year	Percent of Total
1960-01-01	56.4466023090760
1961-01-01	56.0430063746342
1962-01-01	55.6563676636984
1963-01-01	55.2949652340142
1964-01-01	54.9909608212021
1965-01-01	54.7596525697892
1966-01-01	54.2596095160652
1967-01-01	53.8640452424536
1968-01-01	53.5517035094695
1969-01-01	53.2977439267594
1970-01-01	53.0883756704231
1971-01-01	52.6767032680547
1972-01-01	52.3549177658977
1973-01-01	52.1074935566493
1974-01-01	51.9203981160892
1975-01-01	51.7828961170416
1976-01-01	51.4899887158507
1977-01-01	51.2720627918539
1978-01-01	51.1169890049144
1979-01-01	51.0164636097682
1980-01-01	50.9633013331396
1981-01-01	50.7576185928848
1982-01-01	50.6356369124636
1983-01-01	50.5764800496244
1984-01-01	50.5591414973806
1985-01-01	50.5723616752690
1986-01-01	50.4475643806593
1987-01-01	50.3830979592584
1988-01-01	50.3687469665206
1989-01-01	50.3965754470525
1990-01-01	50.4589337824114
1991-01-01	50.5086999725605
1992-01-01	50.6141543489135
1993-01-01	50.7602191546432
1994-01-01	50.9388507967842
1995-01-01	51.1475122249244
1996-01-01	51.1440685405724
1997-01-01	51.2006022631991
1998-01-01	51.3042510623599
1999-01-01	51.4415454274532
2000-01-01	51.6039365850412
2001-01-01	51.6982907225693
2002-01-01	51.8368164899661
2003-01-01	52.0078238906570
2004-01-01	52.1999601548593
2005-01-01	52.4054258054615
2006-01-01	52.4545886913988
2007-01-01	52.5279808808994
2008-01-01	52.6283684929232
2009-01-01	52.7605155496447
2010-01-01	52.9240996475912
2011-01-01	53.0184227510522
2012-01-01	53.1603036644479
2013-01-01	53.3358901952741
2014-01-01	53.5300589731685
2015-01-01	53.7351909312750
2016-01-01	53.8984214744666
2017-01-01	54.0874515868906