| Year | Value | | 2022 | 4.0066505879192 | | 2021 | 4.4865933238807 | | 2020 | 4.3737883559419 | | 2019 | 3.7808472070476 | | 2018 | 4.3155855473278 | | 2017 | 5.2976471193954 | | 2016 | 6.4934547767633 | | 2015 | 7.8226566436654 | | 2014 | 8.8641373352467 | | 2013 | 10.048187090519 | | 2012 | 9.9793719100394 | | 2011 | 9.7892588760779 | | 2010 | 9.8985217146737 | | 2009 | 8.4861872807107 | | 2008 | 6.6065914810512 | | 2007 | 7.8111139981319 | | 2006 | 10.105444696389 | | 2005 | 12.060159550528 | | 2004 | 12.920854074603 | | 2003 | 13.000684734594 | | 2002 | 14.983151977932 | | 2001 | 14.330971604484 | | 2000 | 12.421382616412 | | 1999 | 10.417627683009 | | 1998 | 9.0176868012294 | | 1997 | 9.2023505948271 | | 1996 | 10.198837087096 | | 1995 | 10.684015029396 | | 1994 | 11.370321971061 | | 1993 | 12.400692679669 | | 1992 | 10.504728891503 |
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