Year	Percent of Total
1960-01-01	52.4386041311389
1961-01-01	52.0670061487554
1962-01-01	51.6188847728845
1963-01-01	51.2139165130127
1964-01-01	51.0151101774587
1965-01-01	51.0918833769526
1966-01-01	51.1960390071121
1967-01-01	51.5344311893491
1968-01-01	52.0363787840480
1969-01-01	52.5703789474994
1970-01-01	53.0553162742574
1971-01-01	53.5064190129400
1972-01-01	53.9378541710200
1973-01-01	54.3520268148244
1974-01-01	54.7866946795835
1975-01-01	55.2705100380869
1976-01-01	55.3438830890633
1977-01-01	55.3880887307715
1978-01-01	55.4285922686973
1979-01-01	55.4798226058436
1980-01-01	55.5517172156836
1981-01-01	56.0961362088918
1982-01-01	56.6327391200619
1983-01-01	57.1408581174763
1984-01-01	57.6159821836969
1985-01-01	58.0696731616393
1986-01-01	58.4318039203968
1987-01-01	58.8268050010235
1988-01-01	59.2465670008637
1989-01-01	59.6440266681113
1990-01-01	59.9602814041796
1991-01-01	60.4389452061463
1992-01-01	60.8897245861066
1993-01-01	61.2997069138950
1994-01-01	61.7136191270204
1995-01-01	62.1861518813580
1996-01-01	62.4844999609243
1997-01-01	62.8745064943884
1998-01-01	63.3469184325636
1999-01-01	63.8349374621037
2000-01-01	64.2541523895597
2001-01-01	64.0902192621774
2002-01-01	64.0380182222453
2003-01-01	64.0732693874640
2004-01-01	64.2473326332350
2005-01-01	64.6281326720932
2006-01-01	65.1757427877802
2007-01-01	65.8841649483931
2008-01-01	66.6900913562895
2009-01-01	67.4174953073708
2010-01-01	67.8823907269789
2011-01-01	68.0517125043152
2012-01-01	68.0518728729372
2013-01-01	67.9209575554074
2014-01-01	67.8134356686505
2015-01-01	67.8664317175196
2016-01-01	68.1127040815308
2017-01-01	68.3966922691318