Year Percent 1993-01-01 2.94 1994-01-01 3.79 1995-01-01 3.20 1996-01-01 4.26 1997-01-01 6.29 1998-01-01 12.43 1999-01-01 14.16 2000-01-01 11.36 2001-01-01 12.67 2002-01-01 15.91 2003-01-01 23.12 2004-01-01 28.75 2005-01-01 36.35 2006-01-01 37.95 2007-01-01 51.08 2008-01-01 13.67 2009-01-01 12.25 2010-01-01 17.54 2011-01-01 18.50 2012-01-01 19.09 2013-01-01 19.38 2014-01-01 18.67 2015-01-01 20.81 2016-01-01 21.39