Year % 1988 4.32 1989 4.57 1990 5.99 1991 5.39 1992 4.78 1993 4.47 1994 4.96 1995 5.3 1996 3.33 1997 3.1 1998 2.87 1999 2.85 2000 2.14 2001 2.82 2002 2.3 2003 2.22 2004 2.03 2005 2.39 2006 2.44 2007 2.36 2008 1.84 2009 1.86 2010 2.48 2011 1.73 2012 1.67 2013 1.62 2014 2.27 2015 2.26 2016 2.12 2017 2.08 2018 1.98 2019 2.01 2020 1.8 2021 1.43