| Year | Value | | 2021 | 4.8641202288809 | | 2020 | -5.0459869996571 | | 2019 | 1.6372994341142 | | 2018 | 2.1033651902443 | | 2017 | 2.7653292208214 | | 2016 | 1.6551855820423 | | 2015 | 2.6817008704536 | | 2014 | 2.5335585109996 | | 2013 | 1.4326480171092 | | 2012 | 1.8839186059682 | | 2011 | 1.8011909903146 | | 2010 | 4.0030684643456 | | 2009 | -2.8656705238062 | | 2008 | -1.7237017813976 | | 2007 | 1.781053905876 | | 2006 | 3.3132719884432 | | 2005 | 2.6139934256728 | | 2004 | 3.4854301310496 | | 2003 | 1.8752546084575 | | 2002 | 1.4067508568813 | | 2001 | 1.6431547764227 | | 2000 | 3.4964264168734 | | 1999 | 3.1430313332203 | | 1998 | 3.6338511007083 | | 1997 | 3.8571225172383 | | 1996 | 3.2487515692824 | | 1995 | 3.2497850411272 | | 1994 | 3.7928825841582 | | 1993 | 0.98582682678059 | | 1992 | 2.1184097212053 | | 1991 | 1.3279938953208 | | 1990 | 2.5297232210276 | | 1989 | 3.0958561213535 | | 1988 | 5.515839862409 | | 1987 | 3.7245468506199 | | 1986 | 4.475402208678 | | 1985 | 3.8410180328204 | | 1984 | 5.1821905657479 | | 1983 | 2.6783694909341 | | 1982 | 1.2488082419557 | | 1981 | 1.7359895258476 | | 1980 | 0.92536352880093 | | 1979 | 1.4918631174878 | | 1978 | 4.7013610093679 | | 1977 | 3.3817325680474 | | 1976 | 4.7473759278489 | | 1975 | 0.32464495337199 | | 1974 | -2.5323532643053 | | 1973 | 5.5819095940372 | | 1972 | 5.4503589600842 | | 1971 | 3.2114057206975 |
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