Year % 1990 22.1945464079706 1991 22.451989355904 1992 22.751724574394 1993 23.0167948516716 1994 23.2855712676761 1995 23.5588815480477 1996 23.672750857037 1997 23.6650157586673 1998 23.6288515813669 1999 23.555580583399 2000 23.4477502245692 2001 23.3447368421053 2002 23.2635452353762 2003 23.17897004112 2004 23.110509954676 2005 23.0682133284037 2006 23.0564273940434 2007 23.0745417154988 2008 23.1236442516269 2009 23.215832048493 2010 23.3245122776786 2011 23.4387834832609 2012 23.5663662956201 2013 23.692584924469 2014 23.8211640014182 2015 23.9417436940454 2016 24.049917921381 2017 24.1466845048197 2018 24.2380841354961 2019 24.385059709242 2020 24.6450255772816 2021 24.822950614189 2022 24.9784323391669