Year Number 2002 21.0877 2004 24.75952 2007 28.36226 2009 29.76829 2010 30.10466 2011 26.54315 2012 26.67088 2013 26.63606 2014 26.27563 2015 26.69519 2016 26.24921 2017 26.41088 2018 26.3074