Year Percent 1990 0.44171 1991 0.4082 1992 0.39891 1993 0.40567 1994 0.55528 1995 0.59347 1996 0.68691 1997 0.73285 1998 0.77088 1999 1.07589 2000 1.184 2001 1.14309 2002 1.30568 2003 1.38989 2004 1.20892 2005 1.10647 2006 1.01999 2007 0.94938 2008 0.9646 2009 1.2056 2010 1.39243 2011 1.18283 2012 1.17577 2013 1.10667 2014 0.95191 2015 0.84392 2016 0.80627 2017 0.72166