| Year | Value | | 2020 | 0.81791660762832 | | 2019 | 0.82745832849889 | | 2018 | 0.8477313649011 | | 2017 | 0.86853874232014 | | 2016 | 0.87165477199344 | | 2015 | 0.88799941243153 | | 2014 | 0.90979919791939 | | 2013 | 0.93432604076473 | | 2012 | 0.97905919885843 | | 2011 | 1.0200109193085 | | 2010 | 1.0669415585157 | | 2009 | 1.0967669428533 | | 2008 | 1.1395250646617 | | 2007 | 1.1656911687411 | | 2006 | 1.201745652147 | | 2005 | 1.2476630577782 | | 2004 | 1.2377452508905 | | 2003 | 1.216759832297 | | 2002 | 1.2122537149116 | | 2001 | 1.252898756846 | | 2000 | 1.241651072948 | | 1999 | 1.3781310757982 | | 1998 | 1.4791510196137 | | 1997 | 1.546841680754 | | 1996 | 1.7019845649531 | | 1995 | 1.7552439319916 | | 1994 | 1.4837185754857 | | 1993 | 1.5298872113934 | | 1992 | 1.7549618117568 | | 1991 | 1.8096980872198 |
|