Year	Percent of Total
1960-01-01	46.0169802712838
1961-01-01	45.6223975454745
1962-01-01	45.4595618068704
1963-01-01	45.4418853776111
1964-01-01	45.4329938553781
1965-01-01	45.3727492836828
1966-01-01	45.3364953886693
1967-01-01	45.2922778824991
1968-01-01	45.2723784627061
1969-01-01	45.3243488730699
1970-01-01	45.4811174888272
1971-01-01	47.0414609545044
1972-01-01	48.3073221623693
1973-01-01	49.3239346363345
1974-01-01	50.2522758502233
1975-01-01	51.2125735548633
1976-01-01	51.5972746262454
1977-01-01	52.1700079836778
1978-01-01	52.7668316998417
1979-01-01	53.0665703188511
1980-01-01	52.9127577102410
1981-01-01	53.7881464470256
1982-01-01	54.3726031517547
1983-01-01	54.7460540709486
1984-01-01	55.1366836314875
1985-01-01	55.6713310511881
1986-01-01	55.3069111171026
1987-01-01	54.9466693499698
1988-01-01	54.5563011156207
1989-01-01	53.9956023082720
1990-01-01	53.1879978812459
1991-01-01	53.0086880792917
1992-01-01	52.9424473754604
1993-01-01	53.0613905701643
1994-01-01	53.4107942256426
1995-01-01	53.9643908034512
1996-01-01	54.5854994245803
1997-01-01	55.1264808844762
1998-01-01	55.6860693521800
1999-01-01	56.3642278346247
2000-01-01	57.2019012192602
2001-01-01	58.0692986676354
2002-01-01	59.1243878550441
2003-01-01	60.2725274725275
2004-01-01	61.3641677057357
2005-01-01	62.3065789857114
2006-01-01	63.1654383637261
2007-01-01	63.8242619659028
2008-01-01	64.3288752044646
2009-01-01	64.7838843292168
2010-01-01	65.2426034372403
2011-01-01	65.5074946466809
2012-01-01	65.7976318009879
2013-01-01	66.0765374047531
2014-01-01	66.2702143663031
2015-01-01	66.3593046441309
2016-01-01	66.4042043665030
2017-01-01	66.3547414792488