| Year | Value | | 2021 | -1.276499979573 | | 2020 | -5.3747351211781 | | 2019 | 0.37515186015332 | | 2018 | 0.37081565830476 | | 2017 | 1.3962707081501 | | 2016 | 1.3986738604973 | | 2015 | 4.0563098291936 | | 2014 | 0.35398244376854 | | 2013 | 2.6982624656148 | | 2012 | 1.5667289900792 | | 2011 | 0.75487341535315 | | 2010 | 4.9542570002095 | | 2009 | -5.8170749499726 | | 2008 | -4.6822529677704 | | 2007 | 1.0787630297333 | | 2006 | 0.49746817549258 | | 2005 | 1.2762838667821 | | 2004 | 2.4206437097065 | | 2003 | 1.6166608269581 | | 2002 | 0.45078787071145 | | 2001 | 0.5084989699631 | | 2000 | 2.7391623164364 | | 1999 | 0.89382927307335 | | 1998 | -1.8506323818965 | | 1997 | 0.076545994786741 | | 1996 | 3.4289133753232 | | 1995 | 3.1412918285762 | | 1994 | 2.3359363118995 | | 1993 | 0.89514663319673 | | 1992 | 0.16467440042128 | | 1991 | 2.3973410738782 | | 1990 | 4.732066558276 | | 1989 | 4.456763241631 | | 1988 | 7.3870065612328 | | 1987 | 3.9519201970071 | | 1986 | 4.3009971578189 | | 1985 | 6.2336561452796 | | 1984 | 4.7928453728949 | | 1983 | 2.705697324981 | | 1982 | 3.0854145263083 | | 1981 | 3.2642631808936 | | 1980 | 0.18175659125109 | | 1979 | 2.9399449799456 | | 1978 | 6.5015807562414 | | 1977 | 4.8839916510434 | | 1976 | 4.9789696243601 | | 1975 | 4.3606439843076 | | 1974 | -2.9086445938238 | | 1973 | 7.0200370976815 | | 1972 | 7.827923333961 | | 1971 | 5.7631442723622 |
|