Year	Percent
1968-01-01	69.1747204390834
1969-01-01	68.8487193204452
1970-01-01	68.8421226435321
1971-01-01	68.6785332905397
1972-01-01	68.3085886510326
1973-01-01	68.6443764609645
1974-01-01	67.8080759846357
1975-01-01	67.3412668088861
1976-01-01	67.4410565964458
1977-01-01	67.8033449042088
1978-01-01	68.2607398280448
1979-01-01	68.5088019715006
1980-01-01	68.4986289975572
1981-01-01	68.6651748355662
1982-01-01	68.9514970202105
1983-01-01	69.6026416991368
1984-01-01	69.4400742722572
1985-01-01	69.2102696374880
1986-01-01	69.2025011956661
1987-01-01	69.1516263080440
1988-01-01	69.2616616542637
1989-01-01	69.7366045270528
1990-01-01	70.3374336890016
1991-01-01	71.0072087759609
1992-01-01	71.3479743095988
1993-01-01	71.4210994541352
1994-01-01	71.4827119788713
1995-01-01	71.5878881857480
1996-01-01	72.0775467101877
1997-01-01	72.6410965814944
1998-01-01	72.6702030660136
1999-01-01	72.5651368130549
2000-01-01	72.5650451618340
2001-01-01	72.6552067051208
2002-01-01	72.3802830753597
2003-01-01	72.4308568289486
2004-01-01	72.3808795320426
2005-01-01	72.7352871475799
2006-01-01	73.1808371456420
2007-01-01	73.7364666732302
2008-01-01	73.9346009347593
2009-01-01	74.0935967328611
2010-01-01	74.2051371774431
2011-01-01	74.3976663744535
2012-01-01	73.9869709489748
2013-01-01	74.9276905895126
2014-01-01	75.5964931196702
2015-01-01	76.0838261574425
2016-01-01	76.9638337924005
2017-01-01	77.6270283299155