Year % 1990 23.2379623168179 1991 23.4587670136109 1992 23.6593736593737 1993 23.8888888888889 1994 24.1203703703704 1995 24.3397767492513 1996 24.5500183665973 1997 24.7649955237243 1998 24.9714937286203 1999 25.1826220684352 2000 25.3703373192932 2001 25.5951883718988 2002 25.8636934673367 2003 26.1343416370107 2004 26.3820509213673 2005 26.6086374288584 2006 26.8161778800077 2007 26.9971273149563 2008 27.1538326197877 2009 27.2773222509267 2010 27.3718120805369 2011 27.4863444295579 2012 27.5628003765545 2013 27.5424537302042 2014 27.5949134646284 2015 27.6084745013048 2016 27.6703577512777 2017 27.723623853211 2018 27.7484227129337 2019 27.6774832419257 2020 27.5508694043655 2021 27.4062578945469 2022 27.1894736842105