Year	Percent of Total
1960-01-01	62.8209872870261
1961-01-01	62.2268712226871
1962-01-01	61.8527221531861
1963-01-01	61.6454899658507
1964-01-01	61.5135813840632
1965-01-01	61.4187343481099
1966-01-01	61.4903405863230
1967-01-01	61.5918151069116
1968-01-01	61.7618827613064
1969-01-01	62.0407157956383
1970-01-01	62.4274934645958
1971-01-01	62.9665311342628
1972-01-01	63.4703305483938
1973-01-01	63.9324421031436
1974-01-01	64.3566543653632
1975-01-01	64.7547830809529
1976-01-01	65.0197239962424
1977-01-01	65.3645700132829
1978-01-01	65.7576830644140
1979-01-01	66.1362041943663
1980-01-01	66.4560767158597
1981-01-01	66.7401287287074
1982-01-01	66.9455405098257
1983-01-01	67.0753264248115
1984-01-01	67.1533560346408
1985-01-01	67.1875429578953
1986-01-01	67.0263850653854
1987-01-01	66.8666706369524
1988-01-01	66.7135163668102
1989-01-01	66.5538590025236
1990-01-01	66.3861821936046
1991-01-01	66.1411786034567
1992-01-01	65.9397756420355
1993-01-01	65.8099349934464
1994-01-01	65.7863703763409
1995-01-01	65.8874883310583
1996-01-01	66.1989547606348
1997-01-01	66.5687421132464
1998-01-01	67.0003102742025
1999-01-01	67.4785442137241
2000-01-01	67.9741672940822
2001-01-01	68.2773182229728
2002-01-01	68.5782346969532
2003-01-01	68.8964763439710
2004-01-01	69.2559147545361
2005-01-01	69.6664453923866
2006-01-01	69.9799363825311
2007-01-01	70.3658246568264
2008-01-01	70.7480364363037
2009-01-01	71.0342423377695
2010-01-01	71.1688954933411
2011-01-01	71.0306489940328
2012-01-01	70.7611914613276
2013-01-01	70.3850509267846
2014-01-01	69.9594437487737
2015-01-01	69.5287215421159
2016-01-01	68.9812977621829
2017-01-01	68.4590790907549