Year Number 2008-01-01 0.1522 2009-01-01 0.1618 2010-01-01 0.1901 2011-01-01 0.2285 2012-01-01 0.2746 2013-01-01 0.2753 2014-01-01 0.2752 2015-01-01 0.2366 2016-01-01 0.1891