Year Percent 2005-01-01 37.9562396379461 2006-01-01 38.2356636132716 2007-01-01 38.9232048040072 2008-01-01 39.3886277422066 2009-01-01 39.0199525284580 2010-01-01 38.8473543713146 2011-01-01 38.9669061236822 2012-01-01 38.9033416613902