Year	Percent
1979-01-01	5.28933239773716
1980-01-01	5.05113620101969
1981-01-01	5.00333895168184
1982-01-01	5.91764541212032
1983-01-01	7.62995421941625
1984-01-01	6.87373569782370
1985-01-01	6.40818002030104
1986-01-01	6.40957615313882
1987-01-01	6.41562271229078
1988-01-01	6.01076075572354
1989-01-01	5.20577670513237
1990-01-01	5.38688733356247
1991-01-01	6.99822652638221
1992-01-01	7.69282426388914
1993-01-01	7.96228545586825
1994-01-01	7.32940329327445
1995-01-01	6.21607916094004
1996-01-01	6.44304377969547
1997-01-01	6.43661557667849
1998-01-01	5.79807475070959
1999-01-01	5.30935333720105
2000-01-01	4.91814711418215
2001-01-01	5.17415009668007
2002-01-01	5.00896345497404
2003-01-01	4.87256681104226
2004-01-01	4.36536664443843
2005-01-01	4.11620428906845
2006-01-01	3.99193101821491
2007-01-01	3.90772730377416
2008-01-01	3.91202175586214
2009-01-01	4.56356930859359
2010-01-01	4.39748825842734
2011-01-01	4.36952530492418
2012-01-01	4.35699338705338
2013-01-01	4.69809348392539
2014-01-01	5.13417649270853
2015-01-01	5.22972927436338
2016-01-01	4.96920694485827
2017-01-01	4.80467121729397