| Year | Value | | 2022 | 2.6673884269324 | | 2021 | 1.1956888703833 | | 2020 | -1.1672450176936 | | 2019 | 0.3295620636636 | | 2018 | -1.0371221413154 | | 2017 | 0.69491671161323 | | 2016 | 0.68703712329404 | | 2015 | -2.3018756304564 | | 2014 | 0.24786539236513 | | 2013 | 1.1069855400014 | | 2012 | 0.81608928156237 | | 2011 | 5.8351651957082 | | 2010 | 0.85087864979654 | | 2009 | 2.057937090418 | | 2008 | 5.3002967507259 | | 2007 | 4.4808860861472 | | 2006 | 8.4874857584587 | | 2005 | 3.3778190398824 | | 2004 | 2.3145546223809 | | 2003 | 2.2354366437455 | | 2002 | 2.0410910262021 | | 2001 | 2.3034474834925 | | 2000 | 2.148855327437 | | 1999 | 3.3630363036304 | | 1998 | 3.4463586595527 | | 1997 | 8.9051833911602 | | 1996 | 2.0865738516912 | | 1995 | 2.9568002509262 | | 1994 | 1.4422695880494 | | 1993 | 1.7948614643378 | | 1992 | 2.8584467251446 | | 1991 | 4.3237394435542 | | 1990 | 4.0109840775562 | | 1989 | 5.1699649556257 | | 1988 | 0.23252503399779 | | 1987 | 0.96301264865157 | | 1986 | 0.0066855337242675 | | 1985 | 2.619546299557 | | 1984 | 2.7149047054882 | | 1983 | 2.2915353703471 | | 1982 | 5.9272229820199 | | 1981 | 10.476363196689 | | 1980 | 17.736654804681 |
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