Year % 1997 3.61 1998 2.87 1999 2.08 2000 3.22 2001 1.93 2002 3.16 2003 1.41 2004 2.44 2010 3.8 2011 3.91 2012 3.05 2013 4.84 2014 4.87 2019 7.2 2020 7.7