Year Number 2004-01-01 16.1714 2005-01-01 17.7229 2006-01-01 17.5829 2007-01-01 18.9894 2008-01-01 21.3543 2009-01-01 25.9720 2010-01-01 33.3646 2011-01-01 37.5066 2012-01-01 30.8565