Year Percent 1996-01-01 17.501500000000000 1997-01-01 16.282700000000000 1998-01-01 14.832500000000000 1999-01-01 12.349700000000000 2000-01-01 9.982530000000000 2001-01-01 7.881869999999999 2002-01-01 6.668800000000000 2003-01-01 6.832150000000000 2004-01-01 8.647080000000000 2005-01-01 16.479400000000000 2006-01-01 29.715500000000000 2007-01-01 43.723200000000000 2008-01-01 35.623100000000000 2009-01-01 31.248000000000000 2010-01-01 32.949800000000000 2011-01-01 27.241800000000000 2012-01-01 20.718700000000000 2013-01-01 21.347500000000000 2014-01-01 23.264900000000000 2015-01-01 22.831100000000000 2016-01-01 23.408600000000000 2017-01-01 22.583900000000000