| Year | Value | | 2022 | 10.961882228684 | | 2021 | 3.1332047317449 | | 2020 | -1.568912477409 | | 2019 | 0.98232656988812 | | 2018 | 4.1974588866375 | | 2017 | 1.749896774847 | | 2016 | 1.3047186930318 | | 2015 | 0.72447013487473 | | 2014 | 0.40681608842489 | | 2013 | 0.61008572090503 | | 2012 | 2.0490188352116 | | 2011 | 5.2354159147843 | | 2010 | 0.77700726877769 | | 2009 | 6.3249533623523 | | 2008 | 11.565906838454 | | 2007 | 5.5770639321963 | | 2006 | 3.7000868055555 | | 2005 | 1.8567639257295 | | 2004 | 16.31315079059 | | 2003 | 0.11583011583011 | | 2002 | 8.0503144654087 | | 2001 | 3.8382846386773 | | 2000 | 0.96678235002473 | | 1999 | 0.26512013256035 | | 1998 | 2.2188346883465 | | 1997 | 6.8618235531088 | | 1996 | 5.3746197203028 | | 1995 | -2.9035286574614 | | 1994 | 12.080381890976 | | 1993 | 1.7150912365887 | | 1992 | 9.0311379290717 | | 1991 | -1.819197987984 | | 1990 | 15.23846327247 | | 1989 | 6.4625617114644 | | 1988 | 8.507868010863 | | 1987 | 4.5668494963683 | | 1986 | 5.73355817902 | | 1985 | 9.0905011888749 | | 1984 | 11.860068259472 | | 1983 | 16.460135608993 | | 1982 | 18.296224589119 | | 1981 | 20.506624447129 | | 1980 | 33.0472428985 | | 1979 | 11.11955099805 | | 1978 | 2.0586588570209 | | 1977 | 14.610790265943 | | 1976 | 4.9036868269105 | | 1975 | 8.7877422263188 | | 1974 | 24.987678659561 | | 1973 | 11.764242995987 | | 1972 | 7.5068243858053 | | 1971 | 4.766444232603 | | 1970 | 2.7424094025461 | | 1969 | 4.1305456399797 | | 1968 | 1.7116182572612 | | 1967 | 0.51599587203269 | | 1966 | 2.8662420382165 | | 1965 | 2.1138211382113 | | 1964 | 5.3082191780823 | | 1963 | 0.68965517241379 | | 1962 | 2.6548672566372 |
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