| Year | Value | | 2022 | -1.706495480619 | | 2021 | -2.5301709264721 | | 2020 | -2.4212497099907 | | 2019 | -2.3041386989052 | | 2018 | -2.1229356739247 | | 2017 | -1.9718187474072 | | 2016 | -1.8072307689042 | | 2015 | -1.6392701875804 | | 2014 | -1.4789457111667 | | 2013 | -1.3047820224163 | | 2012 | -1.1462982343373 | | 2011 | 0.98755829677235 | | 2010 | 0.93817319249761 | | 2009 | 0.94376784705119 | | 2008 | 0.87643292186633 | | 2007 | 0.80198274747895 | | 2006 | 0.73099868858394 | | 2005 | 0.6476345756159 | | 2004 | 0.54513966805389 | | 2003 | 0.4064836200247 | | 2002 | 0.25235848278362 | | 2001 | 0.16129866050102 | | 2000 | 1.0982290239574 | | 1999 | 1.7356408271386 | | 1998 | 1.8274547838123 | | 1997 | 1.9586737830747 | | 1996 | 2.0371229286629 | | 1995 | 2.1062573145032 | | 1994 | 2.153530867251 | | 1993 | 2.1649800672888 | | 1992 | 2.1924770416866 | | 1991 | 2.4254881824531 | | 1990 | 3.2519389416962 | | 1989 | 3.8674716367318 | | 1988 | 3.8689102035836 | | 1987 | 3.8571094594654 | | 1986 | 3.8529072039901 | | 1985 | 3.8421294982263 | | 1984 | 3.8267489141565 | | 1983 | 3.7950797094141 | | 1982 | 3.7684867127594 | | 1981 | 3.5047279558472 | | 1980 | 2.5905870335844 | | 1979 | 1.9441949642615 | | 1978 | 1.966517969786 | | 1977 | 2.0258338593437 | | 1976 | 2.0913914127489 | | 1975 | 1.9152245393623 | | 1974 | 1.6788423713746 | | 1973 | 1.6469131071737 | | 1972 | 1.6889865348785 | | 1971 | 1.8951324479844 | | 1970 | 2.5398309365879 | | 1969 | 3.0307680853613 | | 1968 | 3.0127536261231 | | 1967 | 2.965297924528 | | 1966 | 3.0772954165479 | | 1965 | 3.1926615484263 | | 1964 | 3.170313711449 | | 1963 | 3.13299264561 | | 1962 | 3.0839238046841 | | 1961 | 2.6579148082632 |
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