| Year | Value | | 2021 | 5.5820695060829 | | 2020 | -6.3259720076413 | | 2019 | 1.5385978639232 | | 2018 | 1.9791327515732 | | 2017 | 2.699007151344 | | 2016 | 1.8452333721604 | | 2015 | 2.016626837698 | | 2014 | 2.0324539190179 | | 2013 | 0.62353795854429 | | 2012 | 0.060014498817281 | | 2011 | 1.6829540015827 | | 2010 | 3.3719540285328 | | 2009 | -4.4993219898848 | | 2008 | 0.6462369923166 | | 2007 | 3.5039424546847 | | 2006 | 3.6122676442924 | | 2005 | 2.7664708148983 | | 2004 | 3.5277593921482 | | 2003 | 1.9755273114326 | | 2002 | 1.2766123955497 | | 2001 | 2.1375842859538 | | 2000 | 3.6938890644558 | | 1999 | 3.3667820519175 | | 1998 | 3.5949942605073 | | 1997 | 3.4904364531774 | | 1996 | 2.5793630359469 | | 1995 | 2.3061221339012 | | 1994 | 2.3705983195664 | | 1993 | -1.5710332603166 | | 1992 | 1.5767343061591 | | 1991 | 1.6937515379613 | | 1990 | 3.0092704730537 | | 1989 | 3.2395278461496 | | 1988 | 4.450706104272 | | 1987 | 3.1949329118514 | | 1986 | 5.3273702369077 | | 1985 | 2.674048934608 | | 1984 | 2.5069674619339 | | 1983 | 2.094387410446 | | 1982 | 0.93461445762127 | | 1981 | -1.1832543888882 | | 1980 | 0.18269644840497 | | 1979 | 2.8805633121489 |
|