Year | Value | 2021 | 4.5519723552367 | 2020 | 4.8267666636953 | 2019 | 4.3395980275237 | 2018 | 4.2983133339333 | 2017 | 3.5318634728456 | 2014 | 3.7588747559494 | 2013 | 3.7440379749318 | 2012 | 3.8024991734299 | 2011 | 3.8779633848575 | 2010 | 3.9376540397393 | 2009 | 4.2253398922181 | 2008 | 4.3829649106056 | 2007 | 4.2013085074871 | 2006 | 4.3702062815961 | 2005 | 4.4669755998367 | 2004 | 4.3308518888697 | 2003 | 4.3083676381869 | 2002 | 4.2051096594431 | 2001 | 3.7834925116781 | 2000 | 4.0690353553095 | 1999 | 3.5969113509844 | 1998 | 3.5442526826966 | 1997 | 3.3205886915657 | 1996 | 3.2252633511177 | 1995 | 3.0573555064219 | 1994 | 3.1176646043156 | 1993 | 2.7943121456007 | 1992 | 2.5485070956898 | 1991 | 2.5931914446053 |
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