Year % 1988 8.452956 1989 7.669897 1990 7.572112 1991 6.885635 1992 6.313154 1993 6.181393 1994 4.845572 1995 5.230263 1996 3.95873 1997 5.103618 1998 5.151575 1999 5.002307 2000 4.611807 2001 4.671997 2002 4.481588 2003 4.519302 2004 4.673805 2005 4.681125 2006 2.46663 2007 2.4072 2008 2.388898 2009 2.869977 2010 2.636345 2011 2.086662 2012 3.293339 2013 11.72671 2014 0 2015 2.380024 2016 1.519722 2017 0.7753317 2018 0.5988626 2019 0.7263275 2020 0.7692496 2021 0.6643468