Year Number 2008-01-01 1.0776 2009-01-01 4.8669 2010-01-01 8.2559 2011-01-01 12.8565 2012-01-01 17.2277 2013-01-01 18.2154 2014-01-01 18.3072 2015-01-01 20.7128 2016-01-01 16.8106