| Year | Value | | 2021 | 9.0256492927693 | | 2020 | -9.6924871856181 | | 2019 | 1.6139471379807 | | 2018 | 1.3564495492485 | | 2017 | 1.9181946057455 | | 2016 | 1.2538692813686 | | 2015 | 2.3563274581901 | | 2014 | 1.2643803384979 | | 2013 | 1.0148252903659 | | 2012 | 0.56360521120294 | | 2011 | 1.7404848287732 | | 2010 | 1.7068559893217 | | 2009 | -2.8408853687415 | | 2008 | 0.40980264968562 | | 2007 | 2.6299222190496 | | 2006 | 2.0298748370654 | | 2005 | 1.3809327588693 | | 2004 | 2.5953956483845 | | 2003 | 0.90069205766265 | | 2002 | 0.40508543995918 | | 2001 | 2.088911945077 | | 2000 | 2.5236736905922 | | 1999 | 4.2104826006557 | | 1998 | 4.3122261434923 | | 1997 | 2.91295562074 | | 1996 | 1.79864954864 | | 1995 | 2.137141916599 | | 1994 | 2.2356530512449 | | 1993 | 0.44525524371025 | | 1992 | 1.9392036687827 | | 1991 | 0.10769836652409 | | 1990 | 2.7680947651958 | | 1989 | 3.5900327058604 | | 1988 | 5.1927046230712 | | 1987 | 2.8413698721082 | | 1986 | 5.3302870510046 | | 1985 | 2.4586021134776 | | 1984 | 0.9652115902131 | | 1983 | 1.1297969689835 | | 1982 | 1.8987273051072 | | 1981 | 0.531451863412 | | 1980 | 0.37810255922476 | | 1979 | 3.2201671627138 |
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