| Year | Value | | 2022 | -2.5170575672922 | | 2021 | 0.94368816951283 | | 2020 | 0.66610760132079 | | 2019 | 0.53661001782235 | | 2018 | 0.5463519686336 | | 2017 | 0.53219134102444 | | 2016 | 0.5236944630626 | | 2015 | 0.49477257446984 | | 2014 | 0.46948929123715 | | 2013 | 0.48659138706 | | 2012 | 0.48529954509271 | | 2011 | 0.78946899785974 | | 2010 | 0.40200590087472 | | 2009 | 0.40099490520172 | | 2008 | 0.42570555162461 | | 2007 | 0.40545854182554 | | 2006 | 0.393204593401 | | 2005 | 0.30043113256591 | | 2004 | 0.23332845159781 | | 2003 | 0.21273800909834 | | 2002 | 0.09214694962771 | | 2001 | 0.17194664690485 | | 2000 | 0.31952480128691 | | 1999 | 0.36197730491628 | | 1998 | 0.3792609862513 | | 1997 | 0.27990799313781 | | 1996 | 0.099231459697542 | | 1995 | -1.4229670890223 | | 1994 | 0.45784871504276 | | 1993 | 0.68922372406118 | | 1992 | 0.66642157248142 | | 1991 | 0.12694285772619 | | 1990 | 0.065932619254029 | | 1989 | 0.11878837270904 | | 1988 | 0.18506284197792 | | 1987 | 0.29150676532352 | | 1986 | 0.42553255701385 | | 1985 | 0.20009344366934 | | 1984 | 0.28080515877538 | | 1983 | 0.37563768344756 | | 1982 | 0.47154011252384 | | 1981 | 0.58238127629328 | | 1980 | 0.40833049793708 | | 1979 | 0.47850251939754 | | 1978 | 0.53589959926045 | | 1977 | 0.60807263095313 | | 1976 | 0.70946948490331 | | 1975 | 0.4898197463806 | | 1974 | 0.52043158466485 | | 1973 | 0.53733160958175 | | 1972 | 0.56874886712688 | | 1971 | 0.5863441896999 | | 1970 | 0.38801514514673 | | 1969 | 0.43290110895855 | | 1968 | 0.50743131714692 | | 1967 | 0.56847321663912 | | 1966 | 0.68940500404687 | | 1965 | 0.42776081156409 | | 1964 | 0.48899852941918 | | 1963 | 0.53619431413854 | | 1962 | 0.61418813400993 | | 1961 | 0.7087415628398 |
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