Year % of total 1990 4.751868095448519 1991 3.524274842357034 1992 2.9123353293413174 1993 2.835234714003945 1994 2.835234714003945 1995 2.725028409090909 1996 3.010625083300013 1997 3.022252747252747 1998 2.611255574136009 1999 2.3646329365079364 2000 2.1394501800720285 2001 1.7418402258761003 2002 2.0043229886392044 2003 1.8520201503500189 2004 0 2005 0 2006 0 2007 0 2008 0 2009 0 2010 0 2011 0 2012 0 2013 0 2014 0 2015 0 2016 0