Year	Percent
1968-01-01	1.064831224161250
1969-01-01	0.974633193698481
1970-01-01	1.036947983171400
1971-01-01	1.063531096211960
1972-01-01	1.244991016962880
1973-01-01	1.130387414353520
1974-01-01	1.246360832451560
1975-01-01	1.799718034106830
1976-01-01	2.005503096489060
1977-01-01	1.899422945028060
1978-01-01	2.150071208218750
1979-01-01	1.949785227890220
1980-01-01	1.829094604097090
1981-01-01	2.046809743331510
1982-01-01	2.167287090063730
1983-01-01	2.432080255060370
1984-01-01	2.420321717780400
1985-01-01	2.344307987583700
1986-01-01	2.440836041846710
1987-01-01	2.545638384120360
1988-01-01	2.156569891681550
1989-01-01	1.905156142413610
1990-01-01	1.729477745573100
1991-01-01	1.660546743446480
1992-01-01	1.761061849145240
1993-01-01	2.074864669289160
1994-01-01	2.466676848918970
1995-01-01	2.693759840126720
1996-01-01	2.913550717826260
1997-01-01	2.928243115307760
1998-01-01	3.692632869775540
1999-01-01	4.203419218469420
2000-01-01	4.317741682361770
2001-01-01	4.663878859232380
2002-01-01	4.980833944456840
2003-01-01	4.891164888983650
2004-01-01	4.384231570437500
2005-01-01	4.085642781265300
2006-01-01	3.900291243864430
2007-01-01	3.548936829275410
2008-01-01	3.751228379517820
2009-01-01	4.859502700802890
2010-01-01	4.968318287329460
2011-01-01	4.532572876846970
2012-01-01	4.239689582143660
2013-01-01	4.082380405724980
2014-01-01	3.536891431855730
2015-01-01	3.399565737567500
2016-01-01	3.138822290865490
2017-01-01	2.814293962504160