| 1997 total production | 2007 total production | |
| Mean | 8,740,000,000 | 13,300,000,000 |
| Variance | 63,700,000,000,000,000 | 278,000,000,000,000,000 |
| Observations | 30 | 30 |
| Hypothesized Mean Difference | 0 | |
| df | 42 | |
| t Stat | −42.4981 | |
| P (T ≤ t) one-tail | 0.0000000000000000000000000000000000019 | |
| t Critical one-tail | 1.681952 | |
| P (T ≤ t) two-tail | 0.0000000000000000000000000000000000038 | |
| t Critical two-tail | 2.018082 |