Year Number 2004-01-01 8.8428 2005-01-01 8.5956 2006-01-01 8.6025 2007-01-01 8.4279 2008-01-01 7.9199 2009-01-01 7.3766 2010-01-01 7.1460 2011-01-01 6.9920 2012-01-01 5.9610 2013-01-01 5.3966 2014-01-01 4.9207 2015-01-01 4.0138 2016-01-01 2.9181