| Year | Value | | 2022 | 8.2747749023265 | | 2021 | 1.7264775510924 | | 2020 | 0.72491147813138 | | 2019 | 2.0960463532781 | | 2018 | 2.2211146152658 | | 2017 | 1.6259069299173 | | 2016 | 0.017478850590822 | | 2015 | 0.80198200509962 | | 2014 | 4.5192009851695 | | 2013 | 5.2313361417443 | | 2012 | 4.4954531435461 | | 2011 | 4.877998309707 | | 2010 | 5.6627570842002 | | 2009 | 7.8427016770065 | | 2008 | 13.424463550728 | | 2007 | 9.3572445641716 | | 2006 | 11.470596814905 | | 2005 | 13.798294910899 | | 2004 | 12.314815017885 | | 2003 | 9.4475809161698 | | 2002 | 9.1675204850912 | | 2001 | 11.255615709117 | | 2000 | 10.961549659362 | | 1999 | 10.045281729249 | | 1998 | 11.659299774223 | | 1997 | 13.248044079119 | | 1996 | 17.511452481459 | | 1995 | 23.186498110257 | | 1994 | 13.534468727343 | | 1993 | 9.7786007829378 | | 1992 | 21.791168790061 | | 1991 | 28.709291370662 | | 1990 | 19.039752663565 | | 1989 | 16.509808768739 | | 1988 | 20.83253323092 | | 1987 | 16.842420163039 | | 1986 | 11.83506189361 | | 1985 | 15.057419644576 | | 1984 | 11.947427011886 | | 1983 | 32.623708148783 | | 1982 | 90.121332850417 | | 1981 | 37.056341523951 | | 1980 | 18.135170796071 | | 1979 | 9.1884104370098 | | 1978 | 6.007127099949 | | 1977 | 4.1902404526167 | | 1976 | 3.4858333329171 | | 1975 | 17.369202022655 | | 1974 | 30.073629280364 | | 1973 | 15.214034220418 | | 1972 | 4.6011256928086 | | 1971 | 3.0830484140871 | | 1970 | 4.6522974930315 | | 1969 | 2.6293408365833 | | 1968 | 4.0938914310684 | | 1967 | 1.2083403113442 | | 1966 | 0.18288283762153 | | 1965 | 0.6650000005834 | | 1964 | 3.3240331601813 | | 1963 | 2.9316184705135 | | 1962 | 2.6778596874279 | | 1961 | 2.4307939100916 | | 1960 | 0.79020581796007 |
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