Year Number 1994 13.44659 1995 13.36533 1996 13.60308 1997 14.16388 1998 15.51577 1999 14.02143 2000 14.66081 2001 16.40204 2002 16.71901 2003 15.39244 2004 15.69121 2005 15.91329 2006 16.27857 2007 15.41647 2008 15.31323 2009 15.26084 2010 15.30534 2011 15.23899 2012 14.88819 2013 16.32023 2014 15.84546 2015 15.23637 2016 14.86597 2017 14.52395 2018 14.328