Year Number 1999 14.14065 2000 14.30527 2001 14.54672 2002 14.25036 2003 16.17482 2004 15.97246 2005 15.01919 2006 13.89067 2007 14.56587 2009 13.82081 2010 14.14972 2015 16.55146 2016 13.57949