Year	Percent of Total
1960-01-01	56.5103933030810
1961-01-01	56.2767876023282
1962-01-01	56.1401522401800
1963-01-01	56.0307406552960
1964-01-01	55.8701639396137
1965-01-01	55.6349494478547
1966-01-01	55.2470646572945
1967-01-01	54.8253380716725
1968-01-01	54.4062225342403
1969-01-01	54.0524113270398
1970-01-01	53.7947283491338
1971-01-01	53.5058741296701
1972-01-01	53.3188151519327
1973-01-01	53.2110500560574
1974-01-01	53.1469096442773
1975-01-01	53.1049912767883
1976-01-01	53.0704768647652
1977-01-01	53.0752126917073
1978-01-01	53.1089124374818
1979-01-01	53.1658070443394
1980-01-01	53.2385565615598
1981-01-01	53.2515561772506
1982-01-01	53.3111174127350
1983-01-01	53.3919560256804
1984-01-01	53.4669280930340
1985-01-01	53.5235990466570
1986-01-01	53.3973970985612
1987-01-01	53.2631658806444
1988-01-01	53.1434872498191
1989-01-01	53.0778625831581
1990-01-01	53.0889207024897
1991-01-01	52.9540455098066
1992-01-01	52.9461704683815
1993-01-01	53.0303369023403
1994-01-01	53.1604467165262
1995-01-01	53.3184810497912
1996-01-01	53.5277760015558
1997-01-01	53.7466902066589
1998-01-01	54.0059820376153
1999-01-01	54.3552679481815
2000-01-01	54.8131355677856
2001-01-01	55.2510939560592
2002-01-01	55.8112580294365
2003-01-01	56.4395866551509
2004-01-01	57.0502379952819
2005-01-01	57.5935818248505
2006-01-01	58.0762276505378
2007-01-01	58.4519501272396
2008-01-01	58.7621762264900
2009-01-01	59.0700168177615
2010-01-01	59.3996241162547
2011-01-01	59.5806354839227
2012-01-01	59.8219352086635
2013-01-01	60.0827416503518
2014-01-01	60.3124163264582
2015-01-01	60.4957501620032
2016-01-01	60.6166521558857
2017-01-01	60.7269639659387