Year	Percent of Total
1960-01-01	56.6237483831338
1961-01-01	55.4881826856036
1962-01-01	54.4302864250438
1963-01-01	53.4957648733293
1964-01-01	52.7458427716733
1965-01-01	52.2168488451650
1966-01-01	51.7783682930966
1967-01-01	51.5932305973957
1968-01-01	51.6210887239182
1969-01-01	51.7923747661925
1970-01-01	52.0636298497170
1971-01-01	52.4702386728983
1972-01-01	52.8557881331236
1973-01-01	53.2478845864319
1974-01-01	53.7047231806912
1975-01-01	54.2569803137392
1976-01-01	54.8113146203952
1977-01-01	55.4466189460859
1978-01-01	56.1161488069954
1979-01-01	56.7363872405027
1980-01-01	57.2582907525684
1981-01-01	57.6457257122003
1982-01-01	57.9212782764964
1983-01-01	58.0813099478166
1984-01-01	58.1660941391618
1985-01-01	58.2122538194579
1986-01-01	58.0514710122505
1987-01-01	57.9181442247368
1988-01-01	57.7962609348960
1989-01-01	57.6659118507338
1990-01-01	57.5348568109420
1991-01-01	57.2389866936855
1992-01-01	57.0181462888081
1993-01-01	56.8863072723380
1994-01-01	56.8642876727698
1995-01-01	56.9610259287657
1996-01-01	57.3158972289702
1997-01-01	57.7576090638506
1998-01-01	58.2747500247035
1999-01-01	58.8694930745512
2000-01-01	59.5530367722759
2001-01-01	60.1409143209493
2002-01-01	60.8180597180308
2003-01-01	61.6123156997360
2004-01-01	62.4965734927983
2005-01-01	63.4006911797737
2006-01-01	64.0009518738065
2007-01-01	64.5743893697541
2008-01-01	65.0487411003642
2009-01-01	65.3841825755447
2010-01-01	65.5791405071282
2011-01-01	65.5624949038436
2012-01-01	65.4383862449563
2013-01-01	65.2281885665385
2014-01-01	64.9515998258571
2015-01-01	64.6215322703426
2016-01-01	64.1285859979643
2017-01-01	63.6672044560924