Year Months 2007-01-01 4.411877821 2008-01-01 5.763993823 2009-01-01 6.873493213 2010-01-01 5.291255398 2011-01-01 4.741845560 2012-01-01 4.601436178 2013-01-01 4.463266377 2014-01-01 4.859906174 2015-01-01 4.091106842 2016-01-01 3.729198065