| Year | Value | | 2004 | 0.81956673419098 | | 2003 | 2.4534584996585 | | 2002 | 2.4498835271995 | | 2001 | 2.6380782796468 | | 2000 | 3.9291866305748 | | 1999 | 3.6138141006507 | | 1998 | 4.3660117218765 | | 1997 | 5.0685788471758 | | 1996 | 7.0077625766608 | | 1995 | 6.7176933077686 | | 1994 | 7.5684183448799 | | 1993 | 6.7916047348722 |
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