| Year | Value | | 2022 | -1.1504689253234 | | 2021 | -3.1899549005008 | | 2020 | -2.9840768300379 | | 2019 | -2.7802533733727 | | 2018 | -2.5716193468544 | | 2017 | -2.3913363634171 | | 2016 | -2.2121038296873 | | 2015 | -2.0215255305986 | | 2014 | -1.8335795845832 | | 2013 | -1.6436080492074 | | 2012 | -1.460462948722 | | 2011 | 0.83657325667969 | | 2010 | 0.33081359777307 | | 2009 | 0.41523581900065 | | 2008 | 0.41166820613185 | | 2007 | 0.31409962449659 | | 2006 | 0.23768954946529 | | 2005 | 0.18019348089014 | | 2004 | 0.10649237199122 | | 2003 | 0.0055051427222193 | | 2002 | 0.15242085790684 | | 2001 | 0.34794810365138 | | 2000 | 0.72183770458449 | | 1999 | 1.2523762259764 | | 1998 | 1.5276732343935 | | 1997 | 1.5785343555655 | | 1996 | 1.6354042108644 | | 1995 | 1.7147483071654 | | 1994 | 1.814108707065 | | 1993 | 1.9163325318612 | | 1992 | 2.0238836135888 | | 1991 | 2.1612011954668 | | 1990 | 2.3266826457605 | | 1989 | 2.9345212534556 | | 1988 | 3.6480405487928 | | 1987 | 3.8601750863637 | | 1986 | 3.9381606496642 | | 1985 | 3.9927291965186 | | 1984 | 3.9835267420395 | | 1983 | 3.9866926073444 | | 1982 | 3.9835325315906 | | 1981 | 3.7761168914437 | | 1980 | 3.4539925741417 | | 1979 | 3.3230020660183 | | 1978 | 3.3334152218171 | | 1977 | 3.3338765200134 | | 1976 | 3.3341875237873 | | 1975 | 3.2809541778577 | | 1974 | 2.5225726321504 | | 1973 | 1.731063263101 | | 1972 | 1.6236993643587 | | 1971 | 2.9231870276334 | | 1970 | 5.7794240872234 | | 1969 | 7.4397032251328 | | 1968 | 6.5729649753518 | | 1967 | 4.5302735922899 | | 1966 | 3.4646747856438 | | 1965 | 3.457798741728 | | 1964 | 3.4222107675921 | | 1963 | 3.3602489447148 | | 1962 | 3.2246856812135 | | 1961 | 3.1563709825012 |
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