Year	Percent
1978-01-01	2.02007723700628
1979-01-01	2.01105869373852
1980-01-01	1.98230836568164
1981-01-01	2.13785476522347
1982-01-01	2.30792878499896
1983-01-01	2.64718858260245
1984-01-01	2.79242201639162
1985-01-01	2.68000850770843
1986-01-01	2.82634526107455
1987-01-01	2.84027162676793
1988-01-01	2.61424202053771
1989-01-01	2.34417692719345
1990-01-01	2.21308874276924
1991-01-01	2.23706443723862
1992-01-01	2.26287969533204
1993-01-01	2.65971754675410
1994-01-01	2.98321545451682
1995-01-01	3.25259766818277
1996-01-01	3.39116983559531
1997-01-01	3.47427434491836
1998-01-01	4.02916214244300
1999-01-01	4.51880377719142
2000-01-01	4.53607573322591
2001-01-01	4.80828220143118
2002-01-01	5.16747005508109
2003-01-01	5.00542042350281
2004-01-01	4.47031781112410
2005-01-01	4.27680881095449
2006-01-01	3.92916851699929
2007-01-01	3.80009146702657
2008-01-01	3.90935866753801
2009-01-01	4.85687453473894
2010-01-01	4.64404875974955
2011-01-01	4.22139936302201
2012-01-01	4.09578588166300
2013-01-01	3.70522256851490
2014-01-01	3.41022629285787
2015-01-01	3.12924263271809
2016-01-01	2.88302771126596
2017-01-01	2.69211136009936