| Year | Value | | 2022 | 0.43259581952928 | | 2021 | 0.3959281190202 | | 2020 | 0.35593743409178 | | 2019 | 0.31075983262189 | | 2018 | 0.26133801192909 | | 2017 | 0.21881133699434 | | 2016 | 0.18213248664795 | | 2015 | 0.15770386488791 | | 2014 | 0.14727474955336 | | 2013 | 0.13596698190031 | | 2012 | 0.094235910853157 | | 2011 | 0.061851770055409 | | 2010 | 0.043365735290534 | | 2009 | 0.0064575347921967 | | 2008 | 0.055367410311977 | | 2007 | 0.029533100359548 | | 2006 | 0.077482916127075 | | 2005 | 0.01198604088674 | | 2004 | 0.035949505159695 | | 2003 | 0.0036863981129841 | | 2002 | 0.036856508815897 | | 2001 | 0.085638912923521 | | 2000 | 0.039587371225106 | | 1999 | 0.057107068090927 | | 1998 | 0.16597973325579 | | 1997 | 0.24208612344144 | | 1996 | 0.25658496891902 | | 1995 | 0.46482308888496 | | 1994 | 0.6919278082584 | | 1993 | 0.81586961582738 | | 1992 | 0.85978517380712 | | 1991 | 0.80854969397422 | | 1990 | 2.8508691545989 | | 1989 | 0.088121871311757 | | 1988 | 0.050531823738296 | | 1987 | 0.05849025907421 | | 1986 | 0.081348403807496 | | 1985 | 0.15891938187707 | | 1984 | 0.25081128660472 | | 1983 | 0.27941899067431 | | 1982 | 0.21508504147671 | | 1981 | 0.21755594101877 | | 1980 | 3.5270918188915 | | 1979 | 0.26442923711511 | | 1978 | 2.882842449313 | | 1977 | -3.1295954832306 | | 1976 | 1.7645356851542 | | 1975 | 4.927660819125 | | 1974 | 6.6897661261009 | | 1973 | 9.733431421438 | | 1972 | 7.3129765136091 | | 1971 | 11.113027749214 | | 1970 | 5.1329777967456 | | 1969 | 7.9351956799901 | | 1968 | 12.612111213276 | | 1967 | 6.0879236712782 | | 1966 | 6.0218859993055 | | 1965 | 6.4078856684522 | | 1964 | 2.4815169119724 | | 1963 | 12.851885080098 | | 1962 | 2.020270731752 | | 1961 | 5.3905264836202 |
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