Year Number 2007-01-01 24.1744 2008-01-01 35.9313 2009-01-01 34.6103 2010-01-01 33.8177 2011-01-01 31.8032 2012-01-01 27.1136 2013-01-01 27.3118 2014-01-01 25.2972 2015-01-01 23.3157 2016-01-01 20.8058