| Year | Value | | 2022 | 0.44040518714903 | | 2021 | -2.5628080932518 | | 2020 | -1.8328206468965 | | 2019 | 2.8298524018654 | | 2018 | 4.5560822700265 | | 2017 | 1.8798817000133 | | 2016 | 3.5028090853968 | | 2015 | 3.837569364898 | | 2014 | 3.1067405615279 | | 2013 | 7.1568247209473 | | 2012 | 7.6764281020536 | | 2011 | 6.588978450283 | | 2010 | 5.1521559724712 | | 2009 | 5.3118345384519 | | 2008 | 5.5915848899699 | | 2007 | 5.8889604639785 | | 2006 | 5.5683543278476 | | 2005 | 3.7335922383588 | | 2004 | 2.4431372064122 | | 2003 | 2.6101118489861 | | 2002 | 2.7577620921541 | | 2001 | 2.8919328768867 | | 2000 | 3.0153939973284 | | 1999 | 3.1316302163506 | | 1998 | 3.2438367946761 | | 1997 | 3.3569438748598 | | 1996 | 2.864297474403 | | 1995 | 0.85647340249131 | | 1994 | 0.76115375867346 | | 1993 | 2.016512870208 | | 1992 | 19.052040366322 | | 1991 | -22.347973966406 | | 1990 | -27.722224819871 | | 1989 | 3.7274149810882 | | 1988 | 3.8627657840268 | | 1987 | 4.0031536603063 | | 1986 | 4.103069969491 | | 1985 | 4.0507720003843 | | 1984 | 4.3926888771991 | | 1983 | 4.9055719337054 | | 1982 | 4.9542872938132 | | 1981 | 5.1631084666104 | | 1980 | 5.617456160116 | | 1979 | 6.0713047453784 | | 1978 | 6.3561375683001 | | 1977 | 6.4951202241744 | | 1976 | 6.4304517512727 | | 1975 | 6.1693054737779 | | 1974 | 5.9888365017949 | | 1973 | 6.0243908909059 | | 1972 | 6.2136102393174 | | 1971 | 6.7371033824322 | | 1970 | 7.7332915461246 | | 1969 | 8.7021164785325 | | 1968 | 9.201339749558 | | 1967 | 9.4075835472777 | | 1966 | 9.573293164203 | | 1965 | 9.8267217626281 | | 1964 | 10.221450473976 | | 1963 | 10.60334957452 | | 1962 | 10.734267103251 | | 1961 | 10.638253631385 |
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