| Year | Value | | 2022 | 3.4661697221308 | | 2021 | 0.13325138609639 | | 2020 | 0.33887239256214 | | 2019 | 0.26601251546616 | | 2018 | 0.22410324600555 | | 2017 | 0.41733558866683 | | 2016 | 1.7282646332453 | | 2015 | 3.9666462325536 | | 2014 | 3.5892201661666 | | 2013 | 2.7217757771037 | | 2012 | 5.1017218095867 | | 2011 | 4.4745326579584 | | 2010 | 3.5543773456784 | | 2009 | 5.1599682918105 | | 2008 | 8.4000959398746 | | 2007 | 2.2761847800212 | | 2006 | 3.2987484625822 | | 2005 | 2.1682770118372 | | 2004 | 2.743231989267 | | 2003 | 7.9293648746156 | | 2002 | 12.483598008209 | | 2001 | 37.676745451809 | | 2000 | 96.09637569261 | | 1999 | 52.242005185822 | | 1998 | 36.098433162389 | | 1997 | 30.657567572217 | | 1996 | 24.411459215067 | | 1995 | 22.93413441458 | | 1994 | 27.31088179405 | | 1993 | 44.955053759216 | | 1992 | 54.60782150936 | | 1991 | 48.718080675219 | | 1990 | 48.519112996373 | | 1989 | 75.648190102639 | | 1988 | 58.216286541394 | | 1987 | 29.50399724884 | | 1986 | 23.030226114262 | | 1985 | 27.993610742922 | | 1984 | 31.219581512037 | | 1983 | 48.418222080449 | | 1982 | 16.284488046129 | | 1981 | 14.047968671887 | | 1980 | 11.909289383613 | | 1979 | 10.117190869002 | | 1978 | 13.098138583854 | | 1977 | 12.94441387237 | | 1976 | 10.174630116565 | | 1975 | 14.289674294689 | | 1974 | 22.704081622616 | | 1973 | 12.128146459034 | | 1972 | 7.5251179003473 | | 1971 | 9.5216707800485 | | 1970 | 5.1712761201571 | | 1969 | 6.3266814485131 | | 1968 | 4.3176561297104 | | 1967 | 3.81813815731 | | 1966 | 5.4537269277335 | | 1965 | 3.0690706617574 | | 1964 | 4.0342045376431 | | 1963 | 5.939509059224 | | 1962 | 2.8708853146099 | | 1961 | 3.9856205063491 | | 1960 | 1.6765991261128 |
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