| Year | Value | | 2022 | 4.3923328065227 | | 2021 | 4.0038234627262 | | 2010 | 1.8713354538409 | | 2009 | 2.1578109081655 | | 2008 | 1.9476521973012 | | 2007 | 1.9312851320806 | | 2006 | 1.8754066633039 | | 2005 | 2.0085544905938 | | 2004 | 2.2577946895803 | | 2003 | 2.6313386582222 | | 2002 | 2.8221737178592 | | 1996 | 3.1125064024393 | | 1995 | 2.8062739543913 | | 1991 | 6.1945790253561 | | 1990 | 5.9766180976365 | | 1985 | 8.4140662449044 | | 1984 | 5.8359948340288 |
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