Year	Percent
1981-01-01	12.85720779216420
1982-01-01	10.83180977381720
1983-01-01	10.62075364802400
1984-01-01	10.28409821313810
1985-01-01	9.09050118887496
1986-01-01	8.35358666960756
1987-01-01	7.93475407180072
1988-01-01	9.07115875780022
1989-01-01	8.92994142894025
1990-01-01	11.02492595310240
1991-01-01	12.44800856863540
1992-01-01	10.05611674488410
1993-01-01	10.26309982565180
1994-01-01	22.56505269336960
1995-01-01	12.34357851705130
1996-01-01	9.27539060454458
1997-01-01	7.10647242730889
1998-01-01	7.25700989807216
1999-01-01	5.18148779927583
2000-01-01	4.28297638457243
2001-01-01	5.19888525744053
2002-01-01	4.71146543453269
2003-01-01	5.17967781908312
2004-01-01	4.66846622369882
2005-01-01	6.51685393258431
2006-01-01	6.14731922631268
2007-01-01	6.31049228789322
2008-01-01	10.44412837648850
2009-01-01	4.36173524222762
2010-01-01	4.41626896502544
2011-01-01	6.21534176312235
2012-01-01	5.07474300799150
2013-01-01	4.47062514321322
2014-01-01	3.55680984388108
2015-01-01	3.15783117980921
2016-01-01	2.88585107290009
2017-01-01	3.52025688811618