Year Number 1994 36.94502 1996 38.96016 1997 37.77864 2000 35.64983 2001 35.49999 2002 35.74999 2004 37.2 2009 29.74719 2010 31.06842 2011 32.88032 2013 29.76622 2014 30.45495 2015 30.45146 2016 26.9604 2017 25.85525 2018 24.92784