| Year | Multiple regression equations | R2 |
| 2000 | Qi = −5.975 + 0.869Qi-1 + 1.489Ti + 0.565Ri | 0.90 |
| 2001 | Qi = 6.491+ 0.992Qi-1 − 0.679Ti + 0.962Ri | 0.94 |
| 2002 | Qi = −2.382 + 0.951Qi-1 + 0.606Ti + 0.128Ri | 0.96 |
| 2003 | Qi = 0.228 + 0.966Qi-1 + 0.124Ti + 0.977Ri | 0.97 |
| 2004 | Qi = 3.498 + 0.987Qi-1 − 0.312Ti + 0.375Ri | 0.94 |
| 2005 | Qi = −4.808 + 0.941Qi-1 + 0.942Ti + 0.289Ri | 0.96 |
| 2006 | Qi = 0.709 + 0.965Qi-1 + 0.103Ti + 0.452Ri | 0.96 |
| 2007 | Qi = −2.214+ 0.926Qi-1 + 0.583Ti + 0.241Ri | 0.91 |
| 2000-2007 | Qi = 2.962 + 1.011Qi-1 − 0.422Ti + 0.203RiI | 0.99 |