Year	Percent of Total
1960-01-01	55.2053193087804
1961-01-01	54.8488655727848
1962-01-01	54.4700206586151
1963-01-01	54.1243410267340
1964-01-01	53.9031050314107
1965-01-01	53.8422328197626
1966-01-01	53.5893208230902
1967-01-01	53.5063210173718
1968-01-01	53.5388266170422
1969-01-01	53.5990041408193
1970-01-01	53.6322415315397
1971-01-01	53.4207564978955
1972-01-01	53.2120626887400
1973-01-01	53.0100582654661
1974-01-01	52.8423717693558
1975-01-01	52.7277499615944
1976-01-01	52.3495109330023
1977-01-01	52.0608539420295
1978-01-01	51.8356092346122
1979-01-01	51.6373818177870
1980-01-01	51.4452436391328
1981-01-01	51.0844184169467
1982-01-01	50.7792569430291
1983-01-01	50.5230173610205
1984-01-01	50.3142683778067
1985-01-01	50.1443081506854
1986-01-01	49.8547207460758
1987-01-01	49.6446710269269
1988-01-01	49.4946671396561
1989-01-01	49.3886186856437
1990-01-01	49.3189279786545
1991-01-01	49.0949956594068
1992-01-01	48.9360757110193
1993-01-01	48.8301838900251
1994-01-01	48.7633807546308
1995-01-01	48.7238459118931
1996-01-01	48.5296087601749
1997-01-01	48.4061590890256
1998-01-01	48.3362455533764
1999-01-01	48.3024420015006
2000-01-01	48.2929038919593
2001-01-01	48.1580771214446
2002-01-01	48.0863535720907
2003-01-01	48.0710400642518
2004-01-01	48.1152761115476
2005-01-01	48.2242044285448
2006-01-01	48.2169191535616
2007-01-01	48.2875371158907
2008-01-01	48.4265611004125
2009-01-01	48.6187954813729
2010-01-01	48.8494432920379
2011-01-01	48.9849292652220
2012-01-01	49.1749674442656
2013-01-01	49.4058478607790
2014-01-01	49.6681513265325
2015-01-01	49.9576606100484
2016-01-01	50.1439089300755
2017-01-01	50.3715571966002