| Dependent variable | Independent variable | R | R2 | p-value | AIC value |
| bt (1972-2006) | lt | −0.458 | 0.210 | 5.60 × 10−3 | 380 |
| zt | −0.466 | 0.217 | 4.78 × 10−3 | 379 | |
| bt (1998-2006) | lt | −0.606 | 0.368 | 8.35 × 10−2 | 79 |
| zt | −0.078 | 0.006 | 9.41 × 10−2 | 83 |