Year	Percent
1979-01-01	2.50069772055632
1980-01-01	2.67056679802143
1981-01-01	2.15615880490520
1982-01-01	2.84506468318724
1983-01-01	3.24756076192374
1984-01-01	3.29531348686612
1985-01-01	3.49541700134776
1986-01-01	3.54842582419928
1987-01-01	3.21701369510421
1988-01-01	3.30600325984445
1989-01-01	3.15035290045515
1990-01-01	2.89052763981791
1991-01-01	3.85146454480594
1992-01-01	3.85955050376568
1993-01-01	4.76059607385595
1994-01-01	5.59409359505030
1995-01-01	4.09569418801410
1996-01-01	4.71819867239532
1997-01-01	4.42603178146570
1998-01-01	4.46932315432998
1999-01-01	3.50258076296580
2000-01-01	3.16911268314007
2001-01-01	2.96618624287245
2002-01-01	2.95051399490075
2003-01-01	3.01820727971228
2004-01-01	3.03735552813031
2005-01-01	2.89666534350718
2006-01-01	2.77378586327720
2007-01-01	2.63120326888056
2008-01-01	2.00940362811062
2009-01-01	2.87128803458842
2010-01-01	2.62967169814467
2011-01-01	2.88756903691420
2012-01-01	3.11177899682722
2013-01-01	3.18109672030910
2014-01-01	3.80832556937356
2015-01-01	3.54670365836438
2016-01-01	3.60046134034097
2017-01-01	3.72373898334856