Year	Percent of Total
1960-01-01	54.3670089483899
1961-01-01	54.1018416350093
1962-01-01	53.7844343579787
1963-01-01	53.4386820070795
1964-01-01	53.1143255437471
1965-01-01	52.8235637561977
1966-01-01	52.3262125329118
1967-01-01	51.8867919507238
1968-01-01	51.4852106830621
1969-01-01	51.1018104351757
1970-01-01	50.7320745095209
1971-01-01	50.2603958627487
1972-01-01	49.8861864068159
1973-01-01	49.5862808057579
1974-01-01	49.3497545023667
1975-01-01	49.1797973565850
1976-01-01	49.0219973456236
1977-01-01	48.9511756024926
1978-01-01	48.9718179325050
1979-01-01	49.1021978351997
1980-01-01	49.3494883934168
1981-01-01	49.7954914016180
1982-01-01	50.3528849971872
1983-01-01	50.9898085284792
1984-01-01	51.6697426946005
1985-01-01	52.3724753670897
1986-01-01	52.8508926195448
1987-01-01	53.3432707911010
1988-01-01	53.8701142872578
1989-01-01	54.4646532594549
1990-01-01	55.1403183610377
1991-01-01	55.7695553521747
1992-01-01	56.5176680131860
1993-01-01	57.3343071262335
1994-01-01	58.1507776617234
1995-01-01	58.9348160906951
1996-01-01	59.6731775394350
1997-01-01	60.3543413488718
1998-01-01	61.0089650624713
1999-01-01	61.6874753396890
2000-01-01	62.4067100953722
2001-01-01	63.1366479149412
2002-01-01	63.8910613539719
2003-01-01	64.6345624036673
2004-01-01	65.3175883503580
2005-01-01	65.9165485867701
2006-01-01	66.3159075973806
2007-01-01	66.6444513749752
2008-01-01	66.9131803687314
2009-01-01	67.1503579531169
2010-01-01	67.3792619392654
2011-01-01	67.3514866631975
2012-01-01	67.2973600001807
2013-01-01	67.2293603745660
2014-01-01	67.1541017661201
2015-01-01	67.0749027057934
2016-01-01	67.2203548784706
2017-01-01	67.4169706849793