Year Number 2008-01-01 20.3607 2009-01-01 25.1448 2010-01-01 29.7025 2011-01-01 29.9721 2012-01-01 33.1571 2013-01-01 33.3146 2014-01-01 31.5627 2015-01-01 30.7450 2016-01-01 25.5313 2017-01-01 25.5313