| Year | Value | | 2020 | 0.84217947281654 | | 2019 | 0.83063779499753 | | 2018 | 0.83468934560004 | | 2017 | 0.82880242982673 | | 2016 | 0.83004681312594 | | 2015 | 0.83868323035233 | | 2014 | 0.86576958542076 | | 2013 | 0.90243136159894 | | 2012 | 0.94173130629909 | | 2011 | 0.96548950158943 | | 2010 | 0.99735750785492 | | 2009 | 0.99378560886229 | | 2008 | 0.97935610185339 | | 2007 | 0.99997643142366 | | 2006 | 0.97175550460247 | | 2005 | 1.0168063087241 | | 2004 | 0.98126069856449 | | 2003 | 0.99404781630598 | | 2002 | 0.99010201695322 | | 2001 | 0.96514634208891 | | 2000 | 0.99531068279517 | | 1999 | 1.0929499909663 | | 1998 | 1.1209670336465 | | 1997 | 1.0907126497215 | | 1996 | 1.1387477542762 | | 1995 | 1.2028620084955 | | 1994 | 1.2828481950762 | | 1993 | 1.3809598461568 | | 1992 | 1.4725354197688 | | 1991 | 1.6526607565335 |
|