Year	Percent
1979-01-01	4.98838734058612
1980-01-01	4.78080415136267
1981-01-01	4.71598554832806
1982-01-01	5.60737926378280
1983-01-01	7.18460713179493
1984-01-01	6.51872664610805
1985-01-01	6.13611423989930
1986-01-01	6.13423935626528
1987-01-01	6.11086714406158
1988-01-01	5.75790873789196
1989-01-01	5.02223614447967
1990-01-01	5.17653802957543
1991-01-01	6.71419554282979
1992-01-01	7.37054648320264
1993-01-01	7.67400445574521
1994-01-01	7.14558559801084
1995-01-01	6.00819065205209
1996-01-01	6.25077494290314
1997-01-01	6.21896626090218
1998-01-01	5.63227562087913
1999-01-01	5.10119691018265
2000-01-01	4.70437316348012
2001-01-01	4.90785937545229
2002-01-01	4.73099232090697
2003-01-01	4.61053816035191
2004-01-01	4.15470387480771
2005-01-01	3.91653364450189
2006-01-01	3.78035701289009
2007-01-01	3.67319124308304
2008-01-01	3.57819044403670
2009-01-01	4.22333601431032
2010-01-01	4.03451627772761
2011-01-01	4.04442781815861
2012-01-01	4.05845669932215
2013-01-01	4.34088693824689
2014-01-01	4.79909024953466
2015-01-01	4.81811373304156
2016-01-01	4.59799412741121
2017-01-01	4.47623916297437