| Year | Value | | 2021 | 1.2904838315368 | | 2020 | 1.2796532948105 | | 2019 | 1.268822461755 | | 2018 | 1.2579920731933 | | 2017 | 1.247160795644 | | 2016 | 1.2363262584732 | | 2015 | 1.2254903137386 | | 2014 | 1.2087272289514 | | 2013 | 1.191964107123 | | 2012 | 1.1752010223358 | | 2011 | 1.1584379375486 | | 2010 | 1.1416748157203 | | 2009 | 1.1444434937215 | | 2008 | 1.1472122087639 | | 2007 | 1.1499808867652 | | 2006 | 1.1527495647665 | | 2005 | 1.1555182798089 | | 2004 | 1.1582869578101 | | 2003 | 1.1610556358114 | | 2002 | 1.1638243138127 | | 2001 | 1.1665930288551 | | 2000 | 1.1693617068563 | | 1999 | 1.1695587287476 | | 1998 | 1.169755750639 | | 1997 | 1.1699527725303 | | 1996 | 1.1701497944216 | | 1995 | 1.1703468163129 | | 1994 | 1.1705438382042 | | 1993 | 1.1707408600956 | | 1992 | 1.1709378819869 |
|