Year % 1986 40.2201365187713 1987 40.4844402730375 1988 42.0456382252559 1989 42.3920238907849 1990 44.569656996587 1991 46.4206040955631 1992 36.7193430034129 1993 35.2763430034129 1994 39.8573344709897 1995 42.0760085324232 1996 41.3618959044368 1997 33.7102201365188 1998 41.6048583617747 1999 29.4258003412969 2000 18.7866666666667 2001 20.72 2002 16.3267983308288 2003 15.187101145088 2004 15.0830567168883 2005 14.5608333333333 2006 12.893913084832 2007 15.3818501011015 2008 17.1756231436697 2009 13.0080746033842 2010 9.38148993683401 2011 11.2199184470583 2012 12.5850402049247 2013 10.9855861710036 2014 10.8673350376127 2015 11.4499872575296 2016 14.6454318106769 2017 13.6858303184817 2018 12.1148777449182 2019 11.7690653821827 2020 9.85052425129014 2021 9.3378484091001 2022 15.8075088706303 2023 21.0306368304862