Year	Percent of Total
1960-01-01	67.9936933385889
1961-01-01	67.5445200840471
1962-01-01	67.1278410242498
1963-01-01	66.7528484732553
1964-01-01	66.4363434199031
1965-01-01	66.1864968909108
1966-01-01	65.8313754628947
1967-01-01	65.5557450475276
1968-01-01	65.3659248319110
1969-01-01	65.2623034834566
1970-01-01	65.2387036753536
1971-01-01	65.2752859221684
1972-01-01	65.4236561258523
1973-01-01	65.6547176260078
1974-01-01	65.9377144500539
1975-01-01	66.2551591460607
1976-01-01	66.4710963529689
1977-01-01	66.6675023957567
1978-01-01	66.8848127663935
1979-01-01	67.1867118352541
1980-01-01	67.6022832781193
1981-01-01	67.9391196361653
1982-01-01	68.3832833924042
1983-01-01	68.8564350337389
1984-01-01	69.2554572916524
1985-01-01	69.5208839851288
1986-01-01	69.6364731220129
1987-01-01	69.6627124216472
1988-01-01	69.5959563560160
1989-01-01	69.4524312560563
1990-01-01	69.2470487779963
1991-01-01	68.9705242887315
1992-01-01	68.6459169021498
1993-01-01	68.2898616466319
1994-01-01	67.9477080656904
1995-01-01	67.6561745833017
1996-01-01	67.3842207348327
1997-01-01	67.2060651373656
1998-01-01	67.0946122071328
1999-01-01	67.0228306690597
2000-01-01	66.9823413276221
2001-01-01	66.8942157847151
2002-01-01	66.8439532504293
2003-01-01	66.8379824824176
2004-01-01	66.8787722517203
2005-01-01	66.9567230616676
2006-01-01	67.2547115909218
2007-01-01	67.5698619402514
2008-01-01	67.8745838529803
2009-01-01	68.1413076112429
2010-01-01	68.3629690739512
2011-01-01	68.6454809295670
2012-01-01	68.9164085524252
2013-01-01	69.1752291540073
2014-01-01	69.4172017342661
2015-01-01	69.6279252780371
2016-01-01	69.4351859410470
2017-01-01	69.2451003076501