| Year | Value | | 2022 | 6.2476771334388 | | 2021 | 2.2718576250357 | | 2020 | 2.4376088218224 | | 2019 | 2.4528021406273 | | 2018 | 1.0688581131293 | | 2017 | 0.64040914988177 | | 2016 | 0.87419038328912 | | 2015 | 2.676235314199 | | 2014 | 1.8548985036676 | | 2013 | 2.0503471800175 | | 2012 | 2.7352967752956 | | 2011 | 2.9396994630511 | | 2010 | 1.2753804624234 | | 2009 | 3.0436184794 | | 2008 | 5.337806276275 | | 2007 | 0.92140224565011 | | 2006 | 5.1175781601947 | | 2005 | 2.0135395017599 | | 2004 | 0.23364738006758 | | 2003 | 0.62316355737432 | | 2002 | 2.8344226012807 | | 2001 | 4.4197724588115 | | 2000 | 1.2271901297613 | | 1999 | 1.8717450067201 | | 1998 | 3.1707518538691 | | 1997 | 4.7862388186038 | | 1996 | 3.924063727498 | | 1995 | 9.0696907192151 | | 1994 | 35.094461845946 | | 1993 | -3.2065545691587 | | 1992 | 0.016055045871742 | | 1991 | 0.060051330500346 | | 1990 | 1.0993812838361 | | 1989 | -1.6655258955054 | | 1988 | 1.6823326077121 | | 1987 | 13.140499844701 | | 1986 | 7.7700249870353 | | 1985 | 8.5083743439159 | | 1984 | 11.373322090294 | | 1983 | 16.631226410079 | | 1982 | 13.25701986107 | | 1981 | 10.7275 | | 1980 | 9.5517542764287 | | 1979 | 6.5806108190271 | | 1978 | 12.463052344179 | | 1977 | 14.698309158155 | | 1976 | 9.9306505636973 | | 1975 | 13.553329405126 | | 1974 | 17.232933492331 | | 1973 | 10.384748700384 | | 1972 | 8.0929186957962 | | 1971 | 4.0140296180986 | | 1970 | 5.8580858085174 | | 1969 | -1.1015911872741 |
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