Year	Percent of Total
1960-01-01	56.9148871532330
1961-01-01	56.8089029633500
1962-01-01	56.5254323869501
1963-01-01	56.2114744138863
1964-01-01	56.0416990718220
1965-01-01	56.0674357289480
1966-01-01	55.8479469593074
1967-01-01	55.8690887446953
1968-01-01	56.0211450930255
1969-01-01	56.1882779873485
1970-01-01	56.2860684345380
1971-01-01	56.2602165653107
1972-01-01	56.2624186524071
1973-01-01	56.2973407460494
1974-01-01	56.4347060475680
1975-01-01	56.6965846488640
1976-01-01	57.0483425167464
1977-01-01	57.5092590126783
1978-01-01	58.0672331417584
1979-01-01	58.6923217343531
1980-01-01	59.3509538143393
1981-01-01	60.0934873323722
1982-01-01	60.7895222957546
1983-01-01	61.4557027009972
1984-01-01	62.1016719764830
1985-01-01	62.7126611606799
1986-01-01	63.1139413308483
1987-01-01	63.4949396035483
1988-01-01	63.8371539747780
1989-01-01	64.1391348684058
1990-01-01	64.4176123532115
1991-01-01	64.4940137201745
1992-01-01	64.6887848952340
1993-01-01	64.9401199494048
1994-01-01	65.1774844307732
1995-01-01	65.3798874425363
1996-01-01	65.7925021714273
1997-01-01	66.0738236410242
1998-01-01	66.3245962494472
1999-01-01	66.6748779628819
2000-01-01	67.1676521055706
2001-01-01	67.6141477597873
2002-01-01	68.1764328094458
2003-01-01	68.8007079470338
2004-01-01	69.3878432982691
2005-01-01	69.8802208562011
2006-01-01	70.2489582325325
2007-01-01	70.5615858700994
2008-01-01	70.7984825754044
2009-01-01	70.9538180101249
2010-01-01	71.0271890621745
2011-01-01	71.0237798755723
2012-01-01	70.9431659981068
2013-01-01	70.7948700565896
2014-01-01	70.5981208528707
2015-01-01	70.3661970843888
2016-01-01	70.0660164505552
2017-01-01	69.7525661679652