Year	Percent of Total
1960-01-01	56.7275716496280
1961-01-01	56.6483344950937
1962-01-01	56.2558728725440
1963-01-01	55.7750311582521
1964-01-01	55.5005354981028
1965-01-01	55.5280894073583
1966-01-01	55.2202174143875
1967-01-01	55.2821552309752
1968-01-01	55.5434427893707
1969-01-01	55.7729879951388
1970-01-01	55.8814249991377
1971-01-01	55.8136293301946
1972-01-01	55.7615481206575
1973-01-01	55.7447285926806
1974-01-01	55.8460371362874
1975-01-01	56.1216959122415
1976-01-01	56.5924946358462
1977-01-01	57.1886095344048
1978-01-01	57.9094636949656
1979-01-01	58.7253186604765
1980-01-01	59.5967628036503
1981-01-01	60.5781386826616
1982-01-01	61.5076508877648
1983-01-01	62.3957828164231
1984-01-01	63.2321932229451
1985-01-01	63.9809309047169
1986-01-01	64.4423409693317
1987-01-01	64.8180134692594
1988-01-01	65.1062752377080
1989-01-01	65.3467919709492
1990-01-01	65.5868651259777
1991-01-01	65.5328332913109
1992-01-01	65.7110561969849
1993-01-01	66.0017220210602
1994-01-01	66.2558922315203
1995-01-01	66.4235549577445
1996-01-01	66.9569341229923
1997-01-01	67.2408186762589
1998-01-01	67.4515895192364
1999-01-01	67.8296060917899
2000-01-01	68.4625742023468
2001-01-01	69.0651030040569
2002-01-01	69.8854987241075
2003-01-01	70.8254308998727
2004-01-01	71.7024883628554
2005-01-01	72.4134661831714
2006-01-01	72.9013844679579
2007-01-01	73.2913667074869
2008-01-01	73.5570733014317
2009-01-01	73.7066858269640
2010-01-01	73.7515311047533
2011-01-01	73.7059900266319
2012-01-01	73.5597493353795
2013-01-01	73.3217109544214
2014-01-01	73.0094910994939
2015-01-01	72.6382619611355
2016-01-01	72.1765545818009
2017-01-01	71.6818020231928