Year	Percent
1986-01-01	32.3461982117220
1987-01-01	31.1408504105702
1988-01-01	31.3184748096256
1989-01-01	31.7776403110129
1990-01-01	31.0398445574902
1991-01-01	30.1223856049008
1992-01-01	29.9582761536495
1993-01-01	30.1893220819009
1994-01-01	29.1940279601836
1995-01-01	28.4561497468923
1996-01-01	27.0759024445827
1997-01-01	27.7180695518788
1998-01-01	27.7911224574796
1999-01-01	26.8007033441113
2000-01-01	26.5566240703130
2001-01-01	25.8091655788703
2002-01-01	25.3472565596306
2003-01-01	25.4462441508842
2004-01-01	25.1597329625753
2005-01-01	24.0370755555876
2006-01-01	23.7553657116727
2007-01-01	23.5658798285738
2008-01-01	22.8116431431337
2009-01-01	22.7086381588728
2010-01-01	23.5705264489535
2011-01-01	22.5891868801628
2012-01-01	22.7177249066696
2013-01-01	21.8835887707878
2014-01-01	21.0044719875539
2015-01-01	21.1443256204622
2016-01-01	19.5301345522339
2017-01-01	18.3889991461840