| Year | Value | | 2022 | 4.786717047108 | | 2021 | 0.09710076646402 | | 2020 | 4.7666952394423 | | 2019 | 1.5302752896419 | | 2018 | 1.0600741066217 | | 2017 | 0.74435474661241 | | 2016 | 1.4119391547902 | | 2015 | 1.6766308531599 | | 2014 | 4.3099986614911 | | 2013 | 2.9488769463966 | | 2012 | 3.6566204827881 | | 2011 | 4.805389221557 | | 2010 | 7.7891654799118 | | 2009 | 4.6910656774738 | | 2008 | 6.5517669118454 | | 2007 | 2.803738317757 | | 2006 | 4.4158998416956 | | 2005 | 5.6316335135761 | | 2004 | 4.2196878709483 | | 2003 | 7.3235439935181 | | 2002 | 7.5924784983324 | | 2001 | 8.8253892585497 | | 2000 | 4.802288869014 | | 1999 | 0.37226617031193 | | 1998 | 7.9357106981415 | | 1997 | 3.0165054069437 | | 1996 | 4.5407277154024 | | 1995 | 19.872434948347 | | 1994 | 31.841016841638 | | 1993 | 5.4522847373328 | | 1992 | -4.2787431563913 | | 1991 | -3.425287356322 | | 1990 | 0.85787155112474 | | 1989 | 6.1661538461536 | | 1988 | 2.5236593059939 | | 1987 | -13.174472747193 | | 1986 | -17.640424092037 |
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