Year Percent 2001-01-01 11.57 2002-01-01 14.08 2003-01-01 19.74 2004-01-01 23.38 2005-01-01 25.80 2006-01-01 30.34 2007-01-01 45.01 2008-01-01 43.42 2009-01-01 53.54 2010-01-01 54.02 2011-01-01 53.79