Year Number 2004-01-01 7.4556 2005-01-01 7.9799 2006-01-01 8.1268 2007-01-01 7.9217 2008-01-01 7.7264 2009-01-01 7.5393 2010-01-01 4.4782 2011-01-01 4.0582 2012-01-01 3.9565 2013-01-01 3.5586 2014-01-01 4.0452 2015-01-01 3.9422 2016-01-01 4.1158