| Year | Value | | 2022 | 0.60306325017326 | | 2021 | 0.63451757739116 | | 2020 | 0.77686475643871 | | 2019 | 0.69047740069462 | | 2018 | 0.72757756769118 | | 2017 | 0.76215381775842 | | 2016 | 0.86391099358341 | | 2015 | 0.87550783278675 | | 2014 | 0.85972525833079 | | 2013 | 0.82231148989426 | | 2012 | 0.92430561849008 | | 2011 | 0.83727023668878 | | 2010 | 0.7629972456663 | | 2009 | 0.62969822513981 | | 2008 | 0.82330674541483 | | 2007 | 1.0532721661199 | | 2006 | 0.96165669610896 | | 2005 | 1.0172858849172 | | 2004 | 1.3827300626393 | | 2003 | 1.5096943165277 | | 2002 | 1.795567211437 | | 2001 | 1.7816584078499 | | 2000 | 2.0224806081531 | | 1999 | 1.8350123058221 | | 1998 | 1.9065375457 | | 1997 | 1.6387348217001 | | 1996 | 1.7769473693681 | | 1995 | 1.6205059264653 | | 1994 | 1.6543555813106 | | 1993 | 1.7123627054257 | | 1992 | 1.9094371998361 | | 1991 | 3.2315351247489 | | 1990 | 4.2813853753083 | | 1989 | 6.2511950814126 | | 1988 | 6.3412434473818 | | 1987 | 5.8338850879129 |
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