Year Number 1995 31.62624 1996 32.3258 1997 42.3375 1998 34.88593 2001 21.1797 2002 21.174 2003 21.17143 2006 35.11149 2007 36.15298 2008 37.55406 2009 37.49518 2010 37.49069 2011 44.01483 2013 20.54173 2014 19.6666 2015 21.22737 2016 18.82403 2017 20.33355 2018 19.63666