Year	Percent
1968-01-01	0.984987193663076
1969-01-01	0.875763002083390
1970-01-01	0.902957187987659
1971-01-01	0.892118359221402
1972-01-01	1.071250582692870
1973-01-01	0.998833489199654
1974-01-01	1.077068502216430
1975-01-01	1.554791340931940
1976-01-01	1.721896945032820
1977-01-01	1.596249807895480
1978-01-01	1.848471703747870
1979-01-01	1.600424388248180
1980-01-01	1.503643970099400
1981-01-01	1.681432604036100
1982-01-01	1.767964047417470
1983-01-01	2.006146375213690
1984-01-01	1.923556539471630
1985-01-01	1.868998314075740
1986-01-01	1.949806372085040
1987-01-01	2.035584139546020
1988-01-01	1.707779675092050
1989-01-01	1.511715246609850
1990-01-01	1.391476887790000
1991-01-01	1.359780108549440
1992-01-01	1.458048698570960
1993-01-01	1.710723814552660
1994-01-01	2.033935519924300
1995-01-01	2.286487718810540
1996-01-01	2.452469108780590
1997-01-01	2.519852410037650
1998-01-01	3.128078217455570
1999-01-01	3.692528071703470
2000-01-01	3.841701469685940
2001-01-01	4.242265633287730
2002-01-01	4.672578259484950
2003-01-01	4.574406423576440
2004-01-01	4.307432415274800
2005-01-01	4.020654637057250
2006-01-01	3.865178622047000
2007-01-01	3.570488188821480
2008-01-01	3.734083077138140
2009-01-01	4.889630289222250
2010-01-01	4.898238583644080
2011-01-01	4.514014730955470
2012-01-01	4.259592421348930
2013-01-01	4.143013146347650
2014-01-01	3.560546037063440
2015-01-01	3.463800308945500
2016-01-01	3.200586206163590
2017-01-01	2.904189893400980