| Year | Value | | 2022 | 6.1150555010994 | | 2021 | 5.032855746267 | | 2020 | 0.99333702283873 | | 2019 | 2.0872308916201 | | 2018 | 1.2828428844353 | | 2017 | 1.9046561551558 | | 2016 | 0.83600806150621 | | 2015 | -1.0017343277637 | | 2014 | 0.85263049753991 | | 2013 | 1.9012518186058 | | 2012 | 2.3919352131233 | | 2011 | 4.9777356370697 | | 2010 | 3.7333775770425 | | 2009 | 2.95230096381 | | 2008 | 8.1020220696928 | | 2007 | 12.200154444665 | | 2006 | 6.6771579041003 | | 2005 | 6.9255430389016 | | 2004 | 4.6684662236988 | | 2003 | 5.9809781406647 | | 2002 | 5.3410152137741 | | 2001 | 2.6274131420333 | | 2000 | 6.1485433302487 | | 1999 | 7.5382193985139 | | 1998 | 4.5864661654135 | | 1997 | 3.5556709057881 | | 1996 | 7.0947119727605 | | 1995 | 12.210526315789 |
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