Year Number 2003 26.258 2004 27.73489 2005 27.00826 2006 26.11246 2007 25.50813 2008 25.43738 2009 23.05381 2010 26.44469 2011 24.11815 2012 25.03671 2013 22.62245 2014 22.45603 2015 22.07316 2016 22.19245