| Year | Value | | 2019 | 0.26601251546614 | | 2018 | 0.22410324600546 | | 2017 | 0.4173355886668 | | 2016 | 1.7282646332453 | | 2015 | 3.9666462325535 | | 2014 | 3.5892201661667 | | 2013 | 2.7217757771036 | | 2012 | 5.1017218095867 | | 2011 | 4.4745326579584 | | 2010 | 3.5543773456785 | | 2009 | 5.1599682918105 | | 2008 | 8.4000959398746 | | 2007 | 2.2761847800212 | | 2006 | 3.2987484625822 | | 2005 | 2.4077697831569 | | 2004 | 2.7421813294164 | | 2003 | 7.9294100052341 | | 2002 | 12.484018572102 | | 2001 | 37.678020942142 | | 2000 | 96.094113693084 | | 1999 | 52.242350907519 | | 1998 | 36.098433162378 | | 1997 | 30.642980083599 | | 1996 | 24.373088685016 | | 1995 | 22.886133032694 | | 1994 | 27.442528735632 | | 1993 | 45 | | 1992 | 54.340836012862 | | 1991 | 48.803827751196 | | 1990 | 48.519112996456 | | 1989 | 75.6481901022 | | 1988 | 58.216286541168 | | 1987 | 29.503997249272 | | 1986 | 23.030226114375 | | 1985 | 27.98321602596 | | 1984 | 31.230239084947 | | 1983 | 48.433874710312 | | 1982 | 16.257969592885 | | 1981 | 16.387474541823 | | 1980 | 13.048984055597 | | 1979 | 10.266256228003 | | 1978 | 11.650072635779 | | 1977 | 13.014055179756 | | 1976 | 10.671393751374 | | 1975 | 15.362985685126 | | 1974 | 23.321354265282 | | 1973 | 13.011762045022 | | 1972 | 7.8818936066808 | | 1971 | 8.3840253901584 | | 1970 | 5.1299874877938 | | 1969 | 6.326681448513 | | 1968 | 4.3176561297104 | | 1967 | 3.8181381573101 | | 1966 | 5.4537269277334 | | 1965 | 3.0690706617574 | | 1964 | 4.0342045376431 | | 1963 | 5.939509059224 | | 1962 | 2.8708853146098 | | 1961 | 3.9856205063492 | | 1960 | 1.6765991261129 |
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