Year	Percent
1968-01-01	68.3471510909866
1969-01-01	68.0546381497290
1970-01-01	68.0260956200006
1971-01-01	67.8151004303479
1972-01-01	67.3240762543075
1973-01-01	67.7627584970506
1974-01-01	66.8567100875739
1975-01-01	66.0547223073634
1976-01-01	66.0842328384008
1977-01-01	66.4189346402278
1978-01-01	66.7086345367613
1979-01-01	67.0548002776021
1980-01-01	67.0999883068454
1981-01-01	67.1341469539113
1982-01-01	67.3017309593441
1983-01-01	67.7269412634348
1984-01-01	67.5193313115980
1985-01-01	67.3556388350910
1986-01-01	67.2318611014533
1987-01-01	67.1241103285152
1988-01-01	67.4624217661698
1989-01-01	68.1077695395584
1990-01-01	68.8105028765319
1991-01-01	69.4697617827441
1992-01-01	69.7567291144734
1993-01-01	69.5659487256566
1994-01-01	69.3382643599348
1995-01-01	69.2482490795846
1996-01-01	69.5619260585558
1997-01-01	70.0678900243019
1998-01-01	69.5700132512479
1999-01-01	69.0278288766404
2000-01-01	68.9915292922456
2001-01-01	68.8549142199299
2002-01-01	68.3197466442905
2003-01-01	68.4623665797617
2004-01-01	68.8122648795414
2005-01-01	69.3695700956387
2006-01-01	70.0320148566592
2007-01-01	70.7760635358484
2008-01-01	70.8733999572939
2009-01-01	70.1755883385116
2010-01-01	70.2875422991251
2011-01-01	70.8261509852871
2012-01-01	70.6185746100410
2013-01-01	71.7585001992241
2014-01-01	72.7607044512028
2015-01-01	73.3927754342999
2016-01-01	74.4464609847962
2017-01-01	75.3262725309417