Year Number 2005 14.73024 2006 14.54589 2007 14.29825 2008 13.45496 2009 12.65596 2010 12.6035 2011 12.48498 2012 12.78353 2013 12.77789 2014 11.99279 2015 11.26358 2016 10.36068 2017 10.02403 2018 9.86006