| Year | Value | | 2021 | 9.0989446596388 | | 2020 | 9.0996584879764 | | 2019 | 9.1018251310958 | | 2018 | 9.102555458162 | | 2017 | 9.1032659125793 | | 2016 | 9.1039787050987 | | 2015 | 9.1046914976182 | | 2014 | 9.1054213537096 | | 2013 | 9.1061359441111 | | 2012 | 9.1068577800962 | | 2011 | 9.1075731369755 | | 2010 | 9.1080517930063 | | 2009 | 9.1121783018996 | | 2008 | 9.1173151286183 | | 2007 | 9.1224867888071 | | 2006 | 9.1276233603138 | | 2005 | 9.1504738461513 | | 2004 | 9.155620804637 | | 2003 | 9.1593411587666 | | 2002 | 9.2074067505323 | | 2001 | 9.2125779283352 | | 2000 | 9.2177477614167 | | 1999 | 9.2234410400977 | | 1998 | 9.2291343187787 | | 1997 | 9.2348275974598 | | 1996 | 9.2405208761408 | | 1995 | 9.2462141548218 | | 1994 | 9.2519074335028 | | 1993 | 9.2576007121838 | | 1992 | 9.2632939908648 | | 1991 | 9.2689872695458 | | 1990 | 9.2746805482268 |
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