| Year | Value | | 2021 | 5.4675086742058 | | 2020 | -3.9983460837225 | | 2019 | 2.2479130981696 | | 2018 | 2.6116702766386 | | 2017 | 3.7342852214152 | | 2016 | 2.8325559880768 | | 2015 | 3.1807262744843 | | 2014 | 3.3624528932819 | | 2013 | 2.4265846763399 | | 2012 | 3.1210098715745 | | 2011 | 2.7633521162958 | | 2010 | 5.2257887827503 | | 2009 | 0.73683070024914 | | 2008 | 0.14797154175857 | | 2007 | 5.0555156127951 | | 2006 | 5.1941241028407 | | 2005 | 3.562190856664 | | 2004 | 5.4123320361131 | | 2003 | 1.5398562466575 | | 2002 | 3.6476450766438 | | 2001 | 2.0150916972468 | | 2000 | 3.4368663119573 | | 1999 | 2.9368845628491 | | 1998 | 2.0010726361122 | | 1997 | 3.919574607629 | | 1996 | 2.5120557284696 | | 1995 | 3.1052625084401 | | 1994 | 4.8565986688303 | | 1993 | 1.5921220609814 | | 1992 | 2.5277217834137 | | 1991 | 1.2040302512419 | | 1990 | 3.1844093588777 | | 1989 | 3.1196302586914 | | 1988 | 2.6602023152566 | | 1987 | 2.7037397595303 | | 1986 | 3.6108963777906 | | 1985 | 5.4787623963892 | | 1984 | 5.7263525089969 | | 1983 | 4.2573012600267 | | 1982 | 1.0962323412704 |
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