Year Percent 1994 14.54296 1995 17.12258 1996 16.01361 1997 17.29613 1998 18.05398 1999 17.59693 2000 20.51651 2001 15.38327 2002 13.4372 2003 12.98135 2004 13.78546 2005 14.96958 2006 14.99562 2007 19.36685 2008 17.45711 2009 15.59258 2010 15.34034 2011 17.1938 2012 16.58865 2013 16.60628 2014 17.08374 2015 18.44946 2016 17.73464 2017 18.57278