Year Number 2003 27.5503 2004 28.8961 2005 28.66842 2006 27.87439 2007 27.27232 2008 26.74772 2009 23.99712 2010 25.13772 2011 24.7263 2012 25.7089 2013 23.48372 2014 23.23018 2015 22.9846 2016 23.02209