Year Number 2007-01-01 4.4698 2008-01-01 4.8765 2009-01-01 5.7157 2010-01-01 6.1666 2011-01-01 6.3315 2012-01-01 5.9307 2013-01-01 8.3989 2014-01-01 10.2247 2015-01-01 17.7797 2016-01-01 20.3793