Year Number 2003 9.16529 2004 8.71538 2005 8.62308 2006 8.38433 2007 7.12381 2008 6.5 2009 6.50305 2010 6.13353 2011 7.83658 2012 7.44361 2014 7.8063 2015 7.84524 2016 7.68462 2017 7.80156