| Year | Exponential type | Critical value | Half-normal type | Critical value |
| 1998 | 0.9602 | 1.5330 | 1.2778 | 1.8360 |
| 1999 | 0.8646 | 1.5330 | 1.2250 | 1.8360 |
| 2000 | 1.0395 | 1.5330 | 1.3134 | 1.8360 |
| 2001 | 1.063 | 1.5330 | 1.3644 | 1.8360 |
| 2002 | 1.1131 | 1.5330 | 1.3784 | 1.8360 |
| 2003 | 1.0593 | 1.5330 | 1.3501 | 1.8360 |
| 2004 | 1.0288 | 1.5330 | 1.3294 | 1.8360 |
| 2005 | 1.0179 | 1.5330 | 1.3001 | 1.8360 |
| 2006 | 1.0311 | 1.5330 | 1.3080 | 1.8360 |
| 2007 | 0.999 | 1.5330 | 1.3005 | 1.8360 |
| 2008 | 0.9565 | 1.5330 | 1.2659 | 1.8360 |
| 2009 | 0.8596 | 1.5330 | 1.2187 | 1.8360 |
| 2010 | 0.8219 | 1.5330 | 1.2043 | 1.8360 |
| 2011 | 1.0016 | 1.5330 | 1.3144 | 1.8360 |