Year Number 1996 1.96 1997 3.28 1998 3.95 1999 2.23 2000 0.62 2001 2 2002 1.91 2003 4.76 2004 4.92 2005 5.83 2006 4.83 2007 2.23 2008 3.64 2009 8.51 2010 10.82 2011 2.26 2012 8.28 2013 7.81 2014 5.16 2015 7.64 2016 5.72 2017 11.38 2018 9.74 2019 10.89 2020 14