Year % 1995 18.65 1996 16 1997 17.54 1998 16.01 1999 17.98 2000 17.99 2001 17.35 2002 18.09 2003 19.37 2004 19.18 2005 18.39 2006 22.59 2007 22.58 2008 22.62 2009 18.37 2010 22.48 2011 22.54 2012 20.62 2013 23.4 2014 14.28 2015 20.31 2016 19.89 2017 26.67