| Year | Value | | 2004 | 0.039428987382724 | | 2003 | 0.19666080336803 | | 2002 | 0.15951455488928 | | 2001 | 0.19061943871511 | | 2000 | 0.18601435438204 | | 1998 | 0.00088686289986431 | | 1997 | 0.004977303496058 | | 1996 | 0.0037311576538481 | | 1995 | 0.07650289945989 | | 1994 | 2.9110495816501 | | 1993 | 3.2533872377622 | | 1992 | 4.3626328459867 | | 1991 | 1.1858974358974 |
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