| Year | Value | | 2022 | 2.2542609267222 | | 2021 | 0.56266085980226 | | 2020 | 1.0049119426143 | | 2019 | 7.6990526685804 | | 2018 | 8.3435239202376 | | 2017 | 11.423416021186 | | 2016 | -1.2194255611964 | | 2015 | -7.3842620672663 | | 2014 | -3.6121417219563 | | 2013 | -7.7792892430545 | | 2012 | 5.7590628322011 | | 2011 | 3.3927485761699 | | 2010 | 6.5848956289512 | | 2009 | -5.4792696737162 | | 2008 | 4.2701777172632 | | 2007 | -3.683535252654 | | 2006 | 1.3700389668969 | | 2005 | 9.362357660451 | | 2004 | 12.627250974032 | | 2003 | 19.185475171864 | | 2002 | 12.497045726175 | | 2001 | 15.134399837234 | | 2000 | 16.109144839196 | | 1999 | 15.43797757523 | | 1998 | 13.60948294618 | | 1997 | 17.858048128315 | | 1996 | 15.995702211002 | | 1995 | 20.665463739209 | | 1994 | 21.870273063462 | | 1993 | 23.570230011526 | | 1992 | 19.756165094556 | | 1991 | 19.544104699435 | | 1990 | 19.209703399986 | | 1989 | 14.888596375536 | | 1988 | 11.014162178068 | | 1987 | 12.180502724102 | | 1986 | 11.338825548625 |
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