| Year | Value | | 2021 | -2.1971587688543 | | 2020 | -11.144281809613 | | 2019 | 3.9621082441949 | | 2018 | 4.674191184018 | | 2017 | 6.4485069547576 | | 2016 | 6.4530655203233 | | 2015 | 6.9504330070218 | | 2014 | 6.226172829564 | | 2013 | 8.3918942366517 | | 2012 | 8.9837093733824 | | 2011 | 0.95102513890927 | | 2010 | 6.8472436985483 | | 2009 | 5.2981353058304 | | 2008 | 5.3731453165374 | | 2007 | 4.6891032786677 | | 2006 | 4.7596233218511 | | 2005 | 5.098057746653 | | 2004 | 2.1976105161235 | | 2003 | 4.7597062471549 | | 2002 | 2.9915542856108 | | 2001 | 1.4157328071437 | | 2000 | 2.0910549542559 | | 1999 | 4.332011613356 | | 1998 | 10.769355763596 | | 1997 | 6.1123469990044 | | 1996 | 5.1299737362649 | | 1995 | 4.2570008495334 | | 1994 | 6.0066816813739 | | 1993 | 0.45971422338597 | | 1992 | 2.3970112684856 | | 1991 | 0.033285969076616 | | 1990 | 6.0832070027103 | | 1989 | 4.8597616222977 | | 1988 | 7.5490822813093 | | 1987 | 7.5094393712681 | | 1986 | 2.9142925183926 | | 1985 | -6.8700494862952 | | 1984 | -9.8949268427987 | | 1983 | 1.5739808511689 | | 1982 | 2.4638848734679 |
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